I got a great question from Sarah regarding our recent shot of cold. She was curious about why this year was so weird. Seems like this cold, to her, is sticking around longer than normal.
And it has probably felt a bit odd to a lot of folks. And while I look at the record books for the area nearly every day, I wanted to dig into the data to make sure I had the correct answer before I said anything.
So I grabbed the data going back to 1940 and had a look!
THE DATA
First I looked back at the number of days (unofficially, for the general area) that we had a low temperature below 25 degrees for the area.
The average number of consecutive days we dipped below 25 degrees is about 2.5 days. With an average variance of about 1.5 days.
The historical data tells us that we see about 2-3 consecutive days per year with temperatures below 25 degrees overnight and that varies year-to-year by about 1-2 days. So some years it is only 1 day and others years it is up to 5 days in a row of temperatures below 25 degrees.
But what about high temperatures below 40 degrees? We have had a few of those recently.
Historically, those are a little more elusive. We only get 1-2 days per year in succession. With about a 1 day-per-year variance. So, on average, we get 0-3 days in a row with highs at or below 40 degrees.
BACK IN MY DAY….
If you talk to your grandparents they may tell you about “Walking to school in the snow, uphill, both ways, with no boots, just wet socks, old pants and a scarf. Coats hadn’t been invented yet.”
But once they get done ‘yanking your chain’ they might tell you, “seriously, it seems like we got more cold stretches when I was younger…”
And they are right! …. Depending on the decade they are referencing.
The data is really interesting here. Because we see a gradual increase in cooler nights through the 60s, 70s, and 80s. Then a sharp drop into the 90s that has mostly held through present day.
But for afternoon highs below 40 degrees, things are a bit messy. Aside from a drop in the 50s, we see the same gradual rise in teh 60s, 70s, and 80s and then a gradual decrease through the 2000s, then it, sort of, flattens off.
So, we can say, “If your grandparents grew up in the 60s and 70s and were young adults in the 80s… then yeah, they remember it being colder for longer when they were younger.”
RECENT TEMPEATURES
Recently, it really hasn’t been that cold — at least compared to history. Looking at teh charts above, since 2000, we can expect 0-2 days at or below 40 for a high temp each year… and 0-3 days at or below 25 degrees for a low.
As for high temperatures, only two of the final seven days of January were at or below 40 degrees. And they weren’t consecutive. So that is pretty normal. Overnight lows? Three of the final seven days were at or below 25 degrees, but only two of those days were consecutive. Also pretty normal.
So, it looks like this shot of cold has been pretty typical compared to history both recent history and all the way back to 1940.
JUST FOR FUN
For fun, I took a look at the raw data for highs below 50 and lows below 30 to see if I could grab a bigger dataset.
And when you look at these numbers compared to what we have seen recently, it also tallies as “normal” for us for Winter.
Neat stuff!
Hi!
What scale do these records have? That is, are you measuring days for an entire winter (November through February, say) or merely for January?
I ask because what surprised me about this cold snap was having temperatures dip into the teens in late January. Maybe my memory’s faulty, but I don’t remember that happening over the last 20 years — I remember it happening in December or early January, but not late January.