February Review / March Preview

A week ago it wasn't looking very positive for February, but things took a turn at the end of the month.

High Temperatures

Here we Edmonton' have the High temperatures for the last few months.

The first few weeks of February were well below average, and on February 3rd we set a recent record for coldest-High (since 1996) at -18.4°C.

The end of the month felt warm, and it was certainly a change from the rest of the month, but it was actually only a few degrees above the average, and it wasn't anywhere near the top of the range.

By the end of the month we did end up with a total of 7 Highs above freezing, which appear here in orange. That's below the average of 12, but above years like 2014, 2009, 2007 and 2001. 2018 also joins 2014 and 2007 as the only recent February's without any days above 5°C.

We also had 4 Highs below -15°C which is a bit cool, but nothing like the 4 Highs below -20°C in 2011.

This February's average High of -7°C was the 3rd coldest of the last 20 years, after 2007 at -7.3°C and 2014 at -10.1°C. And on the opposite side of things, the average High for February 2016 was 10°C warm than this year, way up at 3°C.

Low Temperatures

For the Low temperatures we set a few recent-coldest records on February 4th, 11th and 12th. Those days were still well, well above the historic records though, which are all down around -40°C.

And it's no surprise that the Lows this month were pretty cold.

The average Low was -17.6°C, which was the 2nd coldest here after 2014 at -19.3°C. We had 12 Lows below -20°C, including 2 below -25°C and 1 below -30°C, and 2014 and 2011 are the only other recent years in that range.

Warm & Cold Days

This chart shows how many warm days (0°C or warmer) and cold days (-20°C or colder) each February has had since 1881.

We first looked at this chart last week, and at that point the forecast was making it sound like February might end up with only 2 or 3 days above freezing. That would have been pretty unusual.

In the end the surprise warmspell pushed February up to 7 warm days, which is below average, but which happens ever 5 years-or-so. And the 12 Lows below -20°C is above average, but isn't too extreme.

Snowfall

In terms of snowfall the International Airport finished the month with 16cm, which is just a bit above the average. So far this winter December has been the only month with snowfall well below the average.

Last year February only had 9cm, but then March and April 2017 were both well above average.

For the winter so far that puts our cumulative snowfall at 76.7cm. That's a bit below average for the beginning of March, although as I type this Environment Canada has issued a winter storm warning for the next few days.

From the red line in this chart we can see how much the March & April snow added to the totals for 2016-2017 last year.

Snowdepth

For snowdepth, the International and Blatchford both jumped up to around 35cm following the storm at the beginning of the month. But by the end of February they had both settled down to 20~25cm, which is right around the average for this year. That's well above where we were at this point last year, when the snow had melted down to almost 0cm.

The beginning of March is when the Big Melt usually starts, and even if we get new snow it doesn't hang around for very long.

This chart shows how the melt might go, although that will obviously depend on how warm the temperatures are and on how much new snow we get. The last 3 years all hit 0cm before the end of March, which is very early. But even after we hit 0cm for the first time, there's always a chance of later spring snowstorms.

March

Here were have the temperature history for March. One thing to keep in mind is that March is not summer. And a lot of the time it isn't even spring. Last March started with a two-week long coldsnap.

In March we average about 2 Lows below -20°C, although the way that plays out is that 2-out-of-3 years don't have any, and then the odd year gets a bunch of them.

On the other hand though, March usually has a lot of days above 0°C. The recent average is 20 days with Highs above freezing, although that's ranged from 2002 with 8 and 2011 with 11, up to 2010 and 2016 with 29.

A cool March after a warm February can sometimes feel like a disappointment - it feels like the weather is going backwards. But February 2018 was pretty chilly, so March basically has to be warmer (fingers-crossed).

Not a warm February

Does it feel like something is missing this February?

February High Temperatures

This table shows High temperatures for every day in February going back to 1999. February 1918 is also included over on the right for some extra history.

The orange squares in the table represent days that had Highs of 0°C or warmer. Last February we had 11 of those warm winter days, in 2016 we had 20, and even a century ago in 1918 there were 11.

In 2018 so far we've had 2 days above 0°C (although one of those was really just a carryover from the day before - Valentine's day was above freezing from midnight to 5AM. At 6AM it dropped to -5°C and then kept falling). Right now the forecasts aren't predicting any big heatwaves before the end of the month, although we might get one or two more warm days.

February Highs of 0°C or Above

This chart shows the number of days with Highs of 0°C or more during February, going back to 1881. Every 4th year here was a leap year and has an extra day, so that skews the counts a tiny bit.

Looking at the 5-Year average we can see that the number of warm February days hasn't actually changed that much over the years. In the 1880s it was around 9 days, and then it climbed up to around 11 days, before dropping in the 1940s. Then it climbed again to hit 15 days in the early late 1980s and again in the late 1990s, and since then it has fallen a bit to a current average of about 12.

The 2 warm days that we have had so far in February 2018 isn't historically-low, but it is pretty uncommon. Since 2000 there have only been 5 years with less than 10 days: 2001 at 6, 2003 at 9, 2007 at 6, 2009 at 5, and 2014 at 3. And since 1881 there have only been 10 other February's with 2-or-less days above freezing - 1881, 1887, 1904, 1922, 1936, 1950, 1962, 1969, 1979, and 1993.

I don't want to give the impression that this is a super-cold February though. As the title says, this February is not-warm, but it also hasn't been extremely cold.

The Warm & Cold Days

This chart shows the 0°C-or-warmer days again, and it also includes the days with Low temperatures that were -20°C-or-colder.

Right now in February we've had 9 Lows below -20°C, which is a bit more than usual - the average is about 6. But recently 2004 had 13 and 2011 had 15, and if we go way back 1979 had 25 and 1936 & 1904 had 28. So February 2018 is not-warm, but it's also not cold.

The 5-Year averages in this chart show how the number of warm days (0°C) and cold days (-20°C) have changed over time. In the 1880s there were typically more cold days, but after that the warm & cold days bounced around each other for decades. By the 1980s the cold days had finally dropped off enough that the warm days were clearly in the lead. Right now the average number of cold days is around 6, while the average number of warm days is double that at 12.

Those are just averages though and sometimes we do still get more cold days than warm: 2009 had 5 warm days and 6 cold; 2011 had 10 warm and 15 cold; 2014 had 3 warm and 13 cold; and now 2018 currently has had 2 warm and 9 cold.

Going forward, lets take a look at March:

First things first: March does still get -20°C days. Recently the average has been about 4 Lows of -20°C or colder, although years like 2002 had 11, and 2011 had 9. But 2010, 2012, 2015 and 2016 all had 0.

But on the flipside the average number of days with Highs of 0°C or warmer is much higher, at 20. Recently that has ranged from 2011 with 11 and 2014 with 13, up to 2010 with 28 and 2016 with 2019.

2002 was the only recent March that had more cold days than warm days (11 cold versus 8 warm) and before that you need to go all the way back to 1932.

So March still isn't summer, but it should feel noticeably more warm than what we've seen this month. We'll be back at the end of February with with the monthly recap to see where things end up.

If you don't like the weather, wait 5 minutes

Today we're going to look at Edmonton's seemingly-erratic weather.

To get a sense of what I'm talking about, here are our High temperatures for the last few months:

November started out really cold, and it ended really warm. December started really warm and ended really cold. January went cold-warm-cold-warm-cold. And February has mostly been pretty cold. Is this sort of variation normal? Can't we ever have nice, "average" temperatures?

This is a theme we've tackled a few times before in:

• How Normal is Average - during the summer about 80% of the days are within ±5°C of the average temperature, but in the winter that range doubles to ±10°C.
• Does Edmonton Get Chinooks - we don't necessarily get chinooks like Calgary does, but we do usually see an an echo of whatever they get.
• 'Tis the season of -20°C - even in the middle of winter we get a lot of warm days to balance off the cold ones.

What we're going to focus on today is how often we swing from warm days to cold days, and then back again.

2017

This is the chart we'll be working with, but it needs a bit of explanation.

This is a chart that we use all the time around here, and it shows daily High temperatures throughout the year. We're going to stick with High temperatures today because they are more variable than the Low temperatures. And so if it feels like our temperatures are behaving erratically then we'll see that more easily with the Highs.

The red and dark blue areas in the chart are the Highs for 2017, and they show whether each day was above or below the average for that time of year. The orange and lighter blue areas in the background show the temperature distribution that Edmonton has seen since 1996, with the warmest, second warmest, coldest and second coldest. The 25th and 75th percentiles are shown as a grey band.

Those 25th and 75th percentiles will be what we're focusing on today. I didn't want to look at just any ol' temperature swing, but wanted to specifically look at when we swing from being warmer than normal to colder than normal, or visa versa. The 25th and 75th percentiles work as handy cutoffs for that.

So with all of that said then: the yellow lines in this chart show every time that the temperature swung from cold (below the 25th percentile) to warm (above the 75th percentile) or the opposite. In 2017 that happened 38 times.

There's a formula controlling all this, and the lines might not exactly match what someone would eye-ball off of the chart, although they should be close. When the temperature spends lots of time hanging around the average that doesn't count as a swing, and if the temperature stays warm or cold for a long time then this chart tries to pick a consistent start or end point. Normally I don't like to invent a bunch of rules for these charts, but we're going to be applying this to 136 years of data, and so it's important to have a standard methodology rather than doing it all by hand.

2017 - Take 2

In 2017 the High temperatures swung between the 25th and 75th percentiles a total of 38 times. But a lot of those happened during the summer when the actual change in temperature was relatively small.

This version of the chart takes all of those swings, and it filters out any where the change in temperature was less than 15°C. That is just an arbitrary cutoff, but a 15°C swing in High temperatures is going to feel like a substantial change no matter where we are during the year - whether it's going from 20°C down to 5°C in June, or from -10°C up to 5°C in February.

Applying the 15°C cutoff filters out the small swings during the summer months, and we are left with a total of 18 swings of 15°C or more for 2017. That includes some very large swings, like in February when things warmed up by 36°C over the course of a week, and in December when temperatures dropped by 31°C over about 2 weeks.

It's important to keep those timeframes in mind, because here we're not necessarily talking about the rapid temperature changes of chinooks (some of Edmonton's largest day-over-day increases are here). Today is more about situations like "It was really warm last week, so why is it absolutely freezing this week?"

2016

As a comparison, here we have 2016. The way that we're measuring things 2016 had a total of 32 swings, compared to 38 in 2017. But when we limit that to the changes of 15°C or more both years had 18. The largest changes for 2016 were a 23°C drop over a week at the end of April, followed by a 26°C warmup in early May.

The beginning of 2016 was the end of a large El Niño, and we can see that for February through late-April the temperatures were mostly well above the average, with only one large temperature swing during those three months.

2015

Here we have 2015. It had 38 swings in total, compared to 32 for 2016 and 38 for 2017. For 15°C swings it had 19, or one more than 2016 and 2017. The largest swings here were a 25°C drop over 4 days in January, and then a 26°C drop over 11 days in February.

The end of 2015 was part of the same El Niño that started 2016, and here again we can see that for October and November the temperatures were mostly above average. But then things did become erratic again briefly during December.

2010 to 2014

And finally, this chart cycles through the 15°C swings for 2010-2014. Here's the summary:

• 2010: 13 swings of 15°C or more. The largest were a 28°C warmup over 12 days in May, and a 27°C drop over 9 days in November
• 2011: 15 swings, including a 30°C warmup over 7 days in January, and a 31°C drop over 9 days in November
• 2012: 14 swings, including a 30°C 5-day drop in January, followed by a 31°C 5-day warmup.
• 2013: 19 swings, including a 26°C 6-day drop in January and a 31°C 6-day warmup in May
• 2014: 20 swings, including a 29°C 11-day warmup in January and a 32°C 9-day warmup in December.

Those are just a few examples, and all the years look pretty similar. With these charts it's tough to compare year-to-year though, or to get a sense of what's going on. That's what we're going to try to do next.

History

This chart takes the same approach to counting temperature swings, and it applies it to all of Environment Canada's data going back to 1881. In the earlier charts today we'd looked at all the temperature swings, and at the swings that were 15°C or more. This chart also adds counts for the 25°C and 30°C swings.

When we look at all of the temperature swings, we see that the 38 in 2017 was not unusual. Years like 2012 and 2014 were quite a bit higher with 46. And since the 1880s the 5-Year average has stayed fairly constant, ranging from the low-30's to the mid-40's.

When we move to the 15°C swings the 18 in 2017 were again very typical. Recently a year like 2010 only had 13 of them, but 2003 had 25. And again, the average has been around 18 since the 1880s.

2017 starts to look a bit unusual when we move to the 25°C and 30°C swings. 2017 had 7 swings of 25°C or more, including 2 of 30°C or more. Recently 2009 and 2011 both had about that many swings. To find a year which had significantly more we need to go all the way back to 1990, with 9 swings of 25°C or more, including 5 of 30°C or more. Going all the way back to the 1880s it looks like the number of large temperature swings has dropped a bit, although that's probably because we don't see High temperatures of -30°C or -40°C anymore.

So 2017 was not exceptionally erratic, but in terms of really large temperature swings it was a little bit on the high-side of what we would typically see.

1990

Here we have 1990, which is the only recent~ish year which had more large swings than 2017 did. 1990 had 41 swings total, 25 of 15°C or more, 9 of 25°C or more, and 5 of 30°C or more.

It looks a lot like all of the other charts from today, but there are a few really extreme months here. From mid-January through late-February there were a series of 30°C swings, and then in November and December the temperatures bounced around constantly.

Summary:

Today we've looked at how often Edmonton's temperature swings from above-average to below-average, or visa versa. This isn't just warm days or cold days, but is how often our weather switches between noticeably warm and noticeably cold.

This discussion was prompted by the question: "Was 2017's weather more erratic than normal?" That's a big question, and so to try to answer it I settled on the approach that we're using here - counting temperature swings between the 25th and 75th percentiles. That choice was arbitrary and it doesn't hold any deep meaning, but it did give us a consistent methodology to apply.

On average we saw that these temperature swings happen about 35 times per year, or about every week-and-a-half. That number varies from year-to-year, and during the summer the temperature swings are smaller than they are during the winter. But overall the numbers have stayed reasonably consistent over the last century, although the very largest swings have decreased a bit in the last few years.

The title today "If you don't like the weather, wait 5 minutes" is a quotation that's originally attributed to Mark Twain. He would have been referring to the weather in New England, but it's also a popular sentiment in Alberta. And it turns out that it's not entirely wrong, but rather than every 5 minutes it's more accurately about every 10 days.

February Rain

Today we're continuing our series on rain-in-months-that-you-wouldn't-expect-to-have-rain, with February.

Previously we've looked at:

• The Cold November Rain?
• January Rain

That means that during the winter of 2017-2018 we've had rain in November, January and now February, but we didn't get any in December so I don't have a writeup for it yet.

Here's the recent history of how often the International Airport has recorded rain during February:

And it's actually pretty sparse, with only 15 rainy days since 1995 that recorded any rain. 

The big standout here is Valentine's Day, 2015 which had a whopping 7.4mm.

In terms of long-term trends:

And again, things are pretty quiet. 

In the 56 years since 1961, there have been 20 that recorded rain during February. Although 7 (now 8 including 2018) of those have been since 2007, so it's possible that the frequency is increasing.

One thing that surprises me is that February is less rainy than January, even though it's usually a few degrees warmer.

January versus February

January has had rain in 33 of the last 56 years, compared to February's 20.

Averages don't have a lot of meaning when the rain is so infrequent, but January's average rainfall is 1.65mm compared to 0.65mm for February. And for a bit more context, March also doesn't get much rain averaging 1.1mm, but then April gets 15mm, and our rainiest month July gets 93mm.

February is 2 or 3 days shorter than January, so there is that to consider. But February is also typically the least snowy of the main winter months, and apparently that applies to rain as well.

Update for February 13, 2018:

Here is the first chart, updated for the rain that fell on February 13, 2018.

The International recorded 0.4mm of rain, and Blatchford recorded 0.7mm of generic precipitation (Blatchford doesn't distinguish between rain and snow, which is why this chart use data for the International).

0.4mm isn't nothing, but it is less than the 1.2mm that fell in 2017 on February 18, and it's also obviously much less than the 7.4mm in 2015.

Birkebeiner Weather

This weekend is the Birkebeiner cross-country ski festival, and the weather looks like it should be pretty good. Let's take a look back at the history of its weather.

Temperature History

These temperatures are for Blatchford, so they aren't necessarily representative of Elk Island where the event is held, but this should at least give an idea of the warm years and the cold years.

1985 was the first time that the Birkebeiner was held in Edmonton, and it was also the coldest with 3 Lows below -25°C and 3 Highs below -20°C. 2008 was another cold one, with 3 Lows below -25°C, and the event was cancelled that year when the windchills were measured down to -46°C.

The warmest Birkebeiner was 2011 with 3 Highs above 5°C, and 3 Lows just below freezing. Recently there had been a string of warm years though, with 2011, 2012, 2013, 2015, 2016 and 2017 all have days above freezing.

The average High temperature has been -4°C, and the average Low -14°C.

Snowdepth

This chart shows the measured snowdepth for each year. These numbers are from the International Airport, which again won't be a perfect match for Elk Island,

Going back through the Birkebeiner's History, it looks like the event was cancelled due to lack of snow in 1987, 2001, 2006, and 2016. (and also in 2008 because of extreme windchills)

In 2018 we're at 34cm of snow, which is the 5th highest in the Birkbeiner's history.

Fresh Snow (or sometimes Rain)

This chart shows how much precipitation - either snow or rain - fell during each Birkbeiner weekend. The snowiest year was 1988 with 18cm falling during the Saturday, and the rainiest was 2015, with 7.4mm falling during the Saturday.