Heating Season Temperature Data and a Couple More Charts

A few weeks ago, we shared the data that indicated our winter temperatures were about as close to average as possible this year.  As we look at the entire heating season, the data looks a bit different.  If these charts look unfamiliar, see the footnote at the bottom of this post for an explanation of the data presented in the charts.

The entire season can be summarized by the position of the red curve at the right side of the chart, where it's apparent that over the entire season our daily average temperatures were considerably warmer than normal.  We accumulated 361 degrees of daily deviation above the average, which means each of the 244 days of our heating season (yep, that's about 8 months!), averaged about 1.5 degrees warmer than normal.

An interesting phenomenon to note is that in early March our heating season was close to the historical norm.  Predominately warmer than normal temperatures since early March have produced our entire cumulative deviation from normal, indicating that the 78 final days of the season averaged over 4.6 degrees warmer than the historical norm.

Recently it occurred to me that all our readers may not have gleaned all the information these temperature charts can communicate, so I present the next chart as an educational tool.

I include the red cumulative deviation curve on these temperature charts for two main reasons: (1) the ability to determine how the data as a cumulative total compares to historical norms, and (2) to recognize trends in the temperature data that may not be easily apparent in the blue daily deviation bars.  On this chart I've added red (warmer) and blue (colder) arrows to illustrate the trends indicated by the red curve (feel free to click the chart for an enlarged view).  In case you hadn't noticed, when the red curve slopes up from left to right, that indicates that the daily deviations from normal have been predominately warmer than average.  Likewise, when the curve slopes down from left to right, colder deviations have predominated.  One can easily recognize at least seven extended temperature trends through the last heating season: four when warmer temperatures prevailed, and three when the daily averages below normal outweighed those above normal.

Since temperatures that were near normal would present a red curve that was roughly flat from left to right, I found it interesting that we seldom observe that characteristic in our temperature data.  Instead, it seems our temperatures are either well above normal or well below normal, leaving very few "normal" days!  This lead me to conjecture that a histogram of the daily temperature deviations for an entire year might look different than the normal distribution, or "bell curve" that one might expect.

To my surprise, the histogram showed our weather to be a lot more "normal" than I expected.  A histogram is a chart in which each bar represents the number of times (or frequency) that a certain temperature deviation was attained.  In the chart above, each bar actually represents a range of temperatures three degrees wide.  For instance, the short bar at the far right indicates that there was one day in which the deviation from average was greater than 21 degrees, but less than or equal to 24 degrees.  The next bar to the left shows five days in which the deviation from average was greater than 18 degrees, but less than or equal to 21 degrees, and so on.  As expected, there aren't many instances at the extreme temperature deviations represented, but there are quite a few days in which the average temperature was very close to the historical average.

The most populated group is that in which the average temperature was the same as the historical average or one or two degrees colder.  The number of days in 2014 when the mean temperature was within 5 degrees colder to 6 degrees warmer than the historical average was 182, just shy of half of the days of the year.  Since 2014 ended a little colder than normal, it might be surprising that 168 days were colder than the historical average, while 179 were warmer, and 18 days matched the historical mean.

Footnote: The blue bars in the upper two charts represent the daily temperature deviation from the historical average for Central Illinois as measured at the Greater Peoria Regional Airport.  Since each day has a historical average high and low temperature, the average of the high and low represents the historical daily average or mean.  The average of the actual high and low temperature represents the actual mean, and the difference between the historical mean and the actual mean represents the daily temperature deviation.  On these charts, all temperatures are shown in degrees Fahrenheit.

Central Illinois Winter Temperature Summary, 2014-2015

Now that winter is officially finished, we can look back at the temperature data and compare reality to what we remembered. I think everyone here in Central Illinois perceived our latest winter to be warmer than the one before it, but prolonged cold (and warm) spells have a way of making comparisons difficult from year to year. The data is presented again this year in the form of combined bar and line charts. The blue bars represent the deviation of the daily mean temperature from the historical average where each bar represents one day. The red curve represents the cumulative deviation from the historical average, and indicates whether the season as a whole was colder or warmer than what we'd typically expect.

The first observation I'd like to bring to your attention is the value of the red curve at the right side of the chart. Including data from March 20, the cumulative deviation from average was -3 degrees. That's almost as close to "normal" as one can get. That means, on average, the daily mean temperature was about 0.03°F colder than the historical average each day. That's a temperature difference most of us can't perceive. It's also probably a smaller number than the error in the measuring equipment at the National Weather Service in Peoria, not to mention the fact that the daily mean temperatures I use are reported as integers that have already been rounded a fraction of a degree each day.

It's also interesting to note that the winter as a whole was warmer than normal until the last week of February, indicated by the red curve crossing the x-axis into negative territory on February 26. February 27 added momentum to that move by recording the largest deviation from average of 28 degrees F below the historical mean. The deviation of 23 degrees F above normal on March 23 recorded the largest deviation on the warm side.

By comparison, we can look again at the data from the winter of 2013-2014 and notice that the cumulative temperature that winter was above normal only a few days all season. I think most of us are happy not to repeat those temperatures this year.

To illustrate just how unusual our temperatures were last winter, I've plotted the cumulative deviation curves for both winters on the same scale on this chart. In both cases, February contributed the largest cumulative degrees below normal, but this year a significant warming trend began on March 7 that carried through the end of the season. Another significant difference this winter was the 18 consecutive days of warmer than normal temperatures beginning on January 15. Those days averaged 10.5 degrees above normal and contributed greatly to counteracting the colder than normal periods.

Since our historical mean temperatures are still low enough to expect heating degree days this time of year, we are technically still in our heating season. We'll continue to compile data to see whether this heating season as a whole was warmer or colder than average.

Winter Weather Summary, 2013-2014

Back on February 13, I showed temperature data for the heating season and winter that showed a colder-than-average trend through that date.  Now that the heating season is most likely behind us, we can look at the data for the full season.  The first chart shows the full winter from December 21 through March 20 and even though the last couple of weeks averaged less than one degree F colder than normal per day, the consistently colder stretch from February 22 through March 6 pushed the cumulative deviation to a total of 532 degrees colder than average.

That means each day of winter averaged 5.9 degrees colder than normal.  February takes the prize for the coldest month with an average daily mean 10 degrees colder than normal.  Anyone suspecting that this winter was colder than normal can rest assured that their suspicions are confirmed by the data.

If we look at the entire heating season, we see a similar trend in that even though the average temperatures warmed a bit in April, the average over the entire season was still over 4 degrees colder than normal.  The cumulative deviation from normal ended the month of April 533 degrees colder than average which means the days between the end of spring and the end of April averaged out to be about equivalent to the historical average.

The effects of winter are still apparent in several places: yew branches that were frozen beyond recovery, rose bushes that didn't survive, and although the almond bush bloomed a couple weeks ago, many of those branches now appear to be dead.  We're happy to concentrate on growing-degree days now, and are hopeful for some harvest from those plants that survived the winter of 2013-2014.

Has this been a normal winter?

Most of us here in Central Illinois have noticed that the temperatures have been running a bit colder than average over the last few weeks, such that some of us have wondered, "Is this winter colder than normal, or are we just spoiled by the last two winters that were milder than average?"  For the sake of this investigation, "normal" temperatures are the simple average of the historical average high and low temperatures for each day.  For instance, the historical average high for February 13 is 36°F and the low is 19°F in Peoria, Illinois, so the "normal" mean temperature for today is 27°F.  Naturally, it's unusual to experience both the average high and low on any given day, so comparing the mean is helpful in determining whether the weather has been warmer or colder than average.

Figure 1 below shows the daily temperature deviation from average since the beginning of winter on December 21.  The blue bars represent the degrees F above or below the daily average, while the red curve is the cumulative deviation from the average over the same period.  Of the 54 days recorded so far, only 17 have been warmer than the historic average, and of the 35 colder days, 25 are 10 or more degrees colder than their average.  January 6 deserves special recognition for recording a mean temperature 31 degrees colder than the historical average!  The mean that day was -9°F, and the high for the day reached -5°F, but alas, that was not the coldest January 6 on record.

Figure 1: December 21 through February 12

The cumulative deviation from average briefly wandered into positive territory twice in December, but has been solidly colder than the average ever since.  Currently, our winter is a cumulative 339 degrees colder than average, which means the daily mean temperature has averaged over 6 degrees colder than average. Since the beginning of 2014, we've averaged over 7 degrees colder than average, and the month of February is averaging over 16 degrees colder than average per day even though February 1 was warmer than the historical average!

Figure 2: September 21 through February 12

In some respects, the entire heating season since last September looks warmer than just the winter data, primarily due to the warm weather from the end of September to the middle of October.  The cumulative deviation is even greater over this period than over the winter period, however, which means our fall season was actually colder than average despite the warm start.  Our 362 degree cumulative deviation works out to about two and a half degrees colder than average per day for the 145 days of fall and winter so far.

So, back to the question in the title, has this been a normal winter?  Yes, it has been normal in the sense that we've had some days warmer than average, and some days colder than average.  But no, it has not been normal in the sense that the temperatures have averaged much colder than the historical average so far. Winter isn't finished, however, as we have 36 more days until spring and a warming trend in the forecast. In order to finish the winter even with the historical average, each of the remaining 36 days would have to average over 9 degrees warmer than average. Plenty of people around here would welcome a trend like that!

(Editor's note: a variation of the word "average" appears 38 times in this post)

What a difference a year makes

A year ago, on March 24, I completed our lawn's first mowing of the season and felt like summer had arrived early.  This year, on March 24, we received 8 inches of snow.  I'm confident summer has not arrived yet.

This photo was taken after two days of melting and it should be obvious that the grass is a long way from its first cutting this season.  In fact, the grass is looking as dormant as it was in January.

On the bright side, the spring yard work looks like it can wait for a few more days.

A few observations on 2012 weather so far

Even though our temperatures here in Central Illinois have seemed consistently above normal since last winter, I thought it might be interesting to look at the data to see just how warm it's been.  The data behind both the charts shown here is the daily mean temperature as measured at the Peoria International Airport; the mean temperature being a simple average of the daily high and low temperatures.

The first chart shows the actual daily means plotted as the red curve, and the historical average daily means plotted in blue.  Since the chart begins at January 1, the mild temperatures we experienced in October, November, and December 2011 are not obvious in this data.  January of this year had a couple of brief cold snaps, February had even fewer days below normal, and most of March was part of a 35-day string of days whose means were significantly above average including 6 record daily highs.  Below normal rainfall accompanied our current 24-day string of above normal temperatures to create drought conditions as severe as any I can remember.

(click to enlarge)

This next chart shows the deviation of the actual mean temperature from the historical mean as the light blue bars that in 2012 have been warmer than the historical mean over 81% of the days so far.  Although the temperature has been much hotter lately, this chart makes it obvious how much warmer than normal the temperatures in March were.  Some days were over 30 degrees F hotter than normal!  No wonder the plants started budding early this spring!

(click to enlarge)

The darker blue dotted curve on the chart represents the cumulative average deviation of the actual mean from the historical mean temperature.  As we approached the end of the warm streak in March and April, the deviation of the cumulative average reached almost 11 degrees F, and even now at July 21 is over 7 degrees F higher than normal.  A year of historically normal temperatures would have zero deviation from the  historic mean, but this year has been so hot that our temperatures have AVERAGED over 7 degrees hotter than normal EVERY DAY!  That's not just statistically significant, that's very unusual!  For reference, 2009 averaged 0.12 degrees F warmer than normal, 2010 averaged 1.85 degrees F warmer than normal, and 2011 averaged 2.07 degrees F warmer than normal, but none of them came close to the 7 degree average deviation so far this year.

I don't predict the weather, but unless the next five months are much colder than normal, our cumulative average should remain significantly above historical levels throughout 2012.

Corn in the backyard 2011, week 3

June 5

Height = 16 inches

Last week's growing degree days = 170

Historical average growing degree days = 121

Growing degree days since planting = 437

Historical average since planting = 368

The corn had a pretty good growth spurt this past week, probably due to the warm temperatures. By contrast, the 2009 crop was planted about the same time, and only managed 5 inches of growth in the same week, but only had 109 growing degree days to help it along. It will be exciting to see how this year's crop progresses in the weeks ahead! Stay tuned!

Hottest day of the year?

By our unofficial monitoring of the thermometer in our backyard, today was that hottest day of 2011 so far.

As far as I'm concerned, we don't need any days hotter than this.

February cycling -- Illinois style

My friend Tim in Pennsylvania posted a video on Facebook of a motorcycle ride he took last Friday in gorgeously uncharacteristic weather there. That prompted me to get out on the bike yesterday to enjoy the mild (55 F) weather here in Illinois. Although it was not as sunny and pleasant here as it was in PA two days earlier, it was still satisfying to enjoy the mild weather, and record the ride on video for Tim's, and your, benefit.


This was my first attempt at recording video while riding (I didn't have the luxury of having someone else do the filming), so I was disappointed that the wind noise makes it hard to hear what I'm saying. I'll leave it to our carefully observant readers to determine the full message I've left for Tim in the video. Give me your best guesses in the comments section.

Thanks for visiting!

After

Twenty-four hours later, the radar indicates that it's all over but the blowing. The skies are clear over our house right now, but the snow continues to redistribute itself.

We haven't seen a plow on our road since yesterday afternoon, and have heard that the interstate highways are shut down except for emergency vehicles. The National Weather Service measured Peoria's snowfall at 15 inches, but we'd be hard pressed to confirm that here.

This is the view this morning to the southeast. Notice the bare spot on the driveway, and the drift closer to the house. I'd estimate the drift at a bit over two feet, and will confirm depth when I take the shovel out later. The tracks on the road were made by our neighbor's tractor that has a big snow auger on the back end (which can be seen at the far right of the photo).

Here's the view to the southwest that shows bare grass by the barn and drifts over three feet closer to the deck. Notice also the bare wood on the deck, where the wind evidently likes to keep things moving.

The view to the west-southwest shows a nice drift next to the snow fence which is probably a result of the wind switch to the northwest last night at about 2 AM. The drift on the deck is big enough that it will probably be ignored for quite a few days.

Finally, the view to the south-southwest shows one major drift in front of the garage and an interesting little drift to the right of the chlorine feeder tube that runs about 50 feet across the yard, driveway, and into the field -- I wonder what caused that one to be formed?

Considering the forecast, things are not as buried as I expected, but reports from around the area indicate it will take awhile to plow all the roads. In the meantime, I guess we'll pop some popcorn and settle into a bit more relaxing.

Thanks for visiting!

Before

The National Weather Service is expecting 16 to 20 inches of snow in our yard by the time this storm is finished tomorrow, so I thought it might be nice to document our conditions on Tuesday morning.

This radar image grabbed from Intellicast indicates we are firmly in the snow band (blue) as of 10:45 AM.

The view from the living room toward the southeast at 10:54 AM.

The view from the family room toward the southwest at the same time.

The view across the deck toward the west-southwest.

And finally the view toward the south-southeast.

The wind is currently out of the northeast, so our best drifting action may be on the southwest side of the house today, although if the wind shifts later we could have nice drifts on several sides. The NWS is predicting 25-35 mph winds for the airport, and we usually get stronger winds than they do, so I think drifting is inevitable, and could be impressive!

I think I could use Noah tomorrow, because we don't normally get snow like this....

More wind than we need

Even though we haven't received a lot of snow, and the wind is only gusting to 40 mph, that's enough to create "white-out" conditions and make us glad we're inside today. On the bright side, the snow fence appears to be doing it's job, and we should have a few nice drifts to play in by the time the storm is done. Here's a short video of the snow in the backyard at 11:32 this morning (which might be more entertaining in full screen mode on YouTube):


If you listen closely, you can hear "God Rest Ye Merry Gentlemen" in the background.

Beautiful sunrise #11, beautiful sunset #15, and a rainbow in between

August 4, 5:38 AM

August 4, 5:29 PM

August 4, 8:06 PM

Evidently a good day for admiring the sky, even if I did have to wipe the condensation off the camera lens each time.

A look back at a cold(?) 2009

Over a month ago, this blog addressed the question, "Was last winter unusually cold?" and in the process we also wondered whether 2009 was colder than average in Peoria, Illinois. When we were living through the weather of 2009, the year seemed colder than normal to us: we received 50% more precipitation than average that year, which probably meant more cloudy days, and a general feeling that more days were colder than average than warmer. Not one to be satisfied with subjective feelings in matters like this, I dug up the data to uncover the truth about 2009.


The vertical bars on the chart below indicate daily temperature deviations. If the actual average temperature was warmer than the historic average for that date, the bar projects upward indicating a positive temperature difference, and vice versa for colder. You can count the bars on the chart, or you can trust me that there were 167 days warmer than average, 178 days colder than average, and 20 days in which the deviation from the historic average was zero degrees. By that measure, there were more days colder than average than days that were warmer than average. But since a day that was 1 degree colder than average counts as much as a day that was 30 degrees warmer than average, does that really tell the whole story?


Another way to look at the data is to look at the cumulative degrees above or below average. That data is reflected in the purple curve that wanders above and below the 0°F line in the chart above. As you can tell, the curve ends the year on the right side of the chart in positive territory -- 42 degrees above average to be exact. Dividing that number by 365 days tells us that each day in 2009 was, on average, 0.12 degrees above the historic average. That may be a small enough number to be statistically insignificant, or at the very least, indiscernible for most people.

So, was 2009 colder than the historic average? That, like most conclusions about weather trends these days, depends on which criteria you use to make the decision. Thanks for visiting, and thanks to Weather Underground for the historic data.

Sunset Crater Volcano National Monument

The weather looked promising for being outside on Friday, so we set out for a couple more National Park Service sites. First stop: Sunset Crater, which is an inactive volcano that still shows quite a bit of evidence of its last eruption. Scientists have used tree ring dating to place the eruption around 1040 to 1100 AD, and since we don't have evidence to the contrary, we'll go with that.

The walking trail around the lava fields at the base of the volcano were simply cinders past the first few hundred feet of concrete. As you can see in the image above, the main cone and the area around it are still pretty sparse even after hundreds of years of vegetation trying to get a foothold.

There were several large expanses like this where the ground was covered by large lava pieces that reminded us of chocolate covered corn flakes. Walking on the cinder trails made a sound similar to what one hears when crushing graham crackers. Why do all our analogies center around food?

At any rate, I continue to be amazed at the lack of vegetation and desolation in some of these areas. It would probably be interesting to study why some areas of a volcano support more vegetation than others, and I would guess available moisture has something to do with it. The mountains in the background of the image above are the San Francisco Peaks which are thought to be the remnants of an older, larger volcano (hence the bowl shape made by the peaks).

This is a hornito, a small vent for lava near the main cone. Amazing to think how many years this thing has been sitting here without much change.

There is no hiking allowed on the cone of Sunset Crater, but there is a hiking trail on Lenox Crater just to the west. We hiked the 300 feet up the cinder slope and were able to find views like this one of Sunset Crater in the background. The slope was pretty steep, and the cinders were very loose, so it was a little work making our way to the top such that we all removed our jackets even though the temperature was in the low 40s. By the time we starting making our way back down we were treated to a light snow shower that lasted until we'd made it all the way back to our van. The snow wasn't a surprise since (a) we experienced heavier snow in Flagstaff the day before, and (b) we could see the snow showers making their way across the San Francisco Peaks before we started our hike. In fact, it was kind of fun and refreshing to enjoy snow knowing that warm temperatures were within easy driving distance. Thanks for visiting!

Was last winter unusually cold?

I've heard several people around our area comment about how cold our last winter was. When one remembers the days in January when the high temperature was barely above 0°F, or the 95 days we spent below 50°F, it seems like the fair-weather crowd has really suffered. Compared to the historic averages for Peoria, Illinois, has it been colder than average? No.

For those readers that are averse to data, graphs, math, and any technical tools that enable us to actually understand our surroundings, I advise you to stop reading right now. You will only be bored and confused, and will likely leave comments about how bored and confused you are. Leave now after you leave happy comments about how warm the weather is. The rest of us will examine the data that led me to the conclusion that our winter in Peoria was warmer than typical.


This first chart shows average mean temperatures for our area from the beginning of August 2009 to the present. That data is represented by the blue curve. The red curve represents the actual mean temperatures we've experienced over that period. When the red curve was lower than the blue curve, the mean temperature was lower than average, while means that are warmer than average are represented by the data that shows the red curve above the blue one. The mean temperature is the average of the daily high and low temperatures, regardless of what time of day those extremes occurred or how long the temperature lingered near those values.

An overview of the chart shows a period at the beginning of October when the mean was well below average followed by about a month and a half that was almost always warmer than average. Likewise there were stretches in January and February that were consistently colder than average, and significant periods in March and April that were warmer than average. How can we tell whether the season as a whole has been colder or warmer than typical?

Answer: the Heating Degree Day. Heating degree days (HDD) are defined relative to a base temperature, and give an indication of how much energy would be required to heat a building on any given day. A common base temperature is 65°F, although almost any base would give you the same kind of relative measure. Given the base temperature of 65°F, our heating season would not technically begin until the average mean temperature drops below 65°F. For Peoria, that condition does not occur until about September 19. The chart below shows data from August 2009 since temperatures were cold enough at the end of that month to actually record HDD at that time. In terms of HDD, our heating season is still ongoing, and won't officially end until about the middle of May. Even though we haven't used our furnace the last few weeks, our historical average mean temperature is still below 65°F.

The purple bars on the chart indicate the difference between the actual HDD and average HDD for each day. The positive bars on the chart indicate the mean temperature was colder than average, and the negative bars indicate mean temperatures warmer than average. The orange curve is the cumulative difference, and is an indication of whether the season to date has required more or less heating energy than average. As you can see, we are over 200 HDD warmer than average for this time of year, although as recently as March 18 our heating season was colder than average.

At this point, a good cold snap in May could bring us right back in line with an average heating season, but I don't know many people that are wishing for that. Thanks for visiting!