Does a cold November mean a cold Winter?

We just had a fairly cold November, which made me wonder if now we need to prepare for a similarly cold winter?

On this blog we do not try to forecast or predict weather. But today we are going to look back at some recent cold Novembers, just to see how the rest of those winters went.

Winter 2017-2018

This chart shows how warm or cold a month is, relative to the 20th century average. The calculation is very simple - it takes the average temperature for all of the days in a month, and compares that to the average for that month for 1901-2000. From this chart we can't tell why a month was cold - if it was just one extreme coldsnap, or if it was cold throughout - we just know if it was above or below average.

We first looked at this chart in How Warm is 2017 - the Months, although this time it's been flipped around to start in July and it has New Year's as the midpoint. Since we're going to be looking at winters this approach will make more sense.

In 2017 July, August and September all averaged about 2°C warmer than the 20th century. October was flat, and then November was -3.9°C colder than the 20th century average. The entire 20th century is a pretty broad reference though, and so the dotted line here is the average of just the last 5 years to provide some recent context.

In the last 5 years our Novembers have actually averaged about 1°C colder than the 20th century, but then the January's and February's have been 4-6°C warmer.

Other Cold Novembers Since 1980

This chart cycles through the 12 other notably cold Novembers that have happened since 1980: 1982, 1984, 1985, 1986, 1990, 1995, 1996, 2003, 2006, 2012, 2013, 2014, and then 2017.

These years range from a small difference of -2.3°C below the 20th century average for 2013, down to a big difference of -8.9°C for 1985. Of these Novembers, the ones that were colder than 2017 were 1984 at -4.5°C, 1985 at -8.9°C, 1996 at -6.6°C, and 2006 at -5.6°C.

As this chart cycles through the years one thing to notice is that they aren't all a sea of below-average blue, and there are quite a few warm months in there. Lets take a closer look, by decade:


The 2010s: 2012, 2013, 2014

Recently we had a string of cold Novembers, in 2012, 2013 & 2014.

• 2012-2013: warm January and February, but the rest were cold
• 2013-2014: warm January, but the rest were cold
• 2014-2015: warm across the board, except for that cold November.

One problem with a cold November is that an early start to winter can make the winter seem extra long. And the winters of 2012-2013 & 2013-2014 not only had cold Novembers, but also cold Marches and Aprils. I don't remember either of them specifically, but those years would have been pushing up against the dreaded "6 months of winter."


The 1990s & 2000s: 1990, 1995, 1996, 2003, 2006

The 1990s and 2000s didn't have very many cold Novembers, but there were a few notable ones here:

• 1990-1991: cold November & December, but a warm January and a very warm February
• 1995-1996: pretty cold across the board. 1996 was the coldest year in Edmonton since the 1950's, possibly due to some volcano eruptions?
• 1996-1997: the second half of 1996, and again pretty cold. February 1997 was warm, though.
• 2003-2004: generally warm, with November as the only cold outlier.
• 2006-2007: cold November followed by a warm December & January.

The 1980s: 1982, 1984, 1985, 1986

And the 1980s had a group of cold Novembers all in quick succession, in 1982, 1984, 1985 & 1986.

• 1982-1983: generally warm, with November as a cold outlier.
• 1984-1985: cold November & December, but warm January & March
• 1985-1986: really cold November, but really warm December, January & March
• 1986-1987: really warm January, February & March.

Summary

So does the cold November of 2017 mean that we need to brace for an extra-cold winter this year? The good news is that there doesn't seem to be a connection.

Of the 12 winters that we've looked at here, 7 of them were warmer during December-April than the average for 1980-through-2016. The 5 that were colder were 1984-1985, 1995-1996, 1996-1997, 2012-2013 and 2013-2014 (although unfortunately those last 2 were very recent). 7-out-of-12 warm versus 5-out-of-12 cold is basically a flip of the coin.

And all of the winters here (except 1995-1996) had at least one genuinely warm month after November, and most winters had a few of them. "Warm" is relative of course, and it really means "warm for Edmonton", but 4°C or 6°C above average at least takes the edge off of things.

We shouldn't treat this as a prediction, but just because we had a cold November doesn't mean that we need to worry that the rest of the winter will follow suit.