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| The summer of 2025 has been hot, but cooler, more autumnal weather has arrived earlier than in recent years. |
Sure, we're still going to have summer-like days. We'll still probably have a few afternoons that get into the 80s. Maybe we'll have a couple humid days or stuffy night or two, but I think summer is done.
Fingers crossed, we might be done with the big heat waves, and the sometimes week long series of nights in which it's almost impossible to sleep without air conditioning.
This is all subjective, of course. Just because I decide summer is over doesn't mean it is.
The widely accepted unofficial end of summer is this weekend - Labor Day. Astronomically, summer doesn't end here until 2:19 p.m. eastern time September 22.
But we all have our own sense of when summer is over. The recent cool days, a rather chilly forecast, and an long term expected weather pattern that doesn't scream heat waves has me sticking a fork in summer.
It's not just me. Down in the nation's capital, the folks at the Washington Post Capital Weather Gang have also declared that summer is over in DC.
"By our meteorological definition, summer ends when there's no longer a realistic chance of three straight days of 90 degrees or higher. This year, we think we've reached that point," the Weather Gang announced on Wednesday. .
I don't have a distinct measure for Vermont. Maybe it's when I think another 90 degree day won't hit until next summer.
That's OK, we've had enough of 'em this year. With 17 such days as measured in Burlington, we're in the top ten list of most 90 degree days in a single year. Plus, there's always the chance I'm wrong. A few (but not all!) computer models bring us back to 90 degrees around September 10. You never know.
I usually figure a season has begun or ended through the lens of hindsight. The second half of this August in Vermont has been chilly, at least compared to recent Augusts. Ever since a strong, autumn-like cold front sliced through the Green Mountain State on August 17, the consistent warmth of this summer disappeared.
Eight of the last 11 days have been below normal. At least below the "new normal" that has arrived. This "new normal" is toastier than the 20th century average, thanks to climate change. The kind of late August we're having this year would have been typical, even a tad on the warm side if the same series of days had happened, say, in 1960 or 1970 or even 1980.
LONGER CLIMATE CHANGED SUMMERS
Still, this August is also breaking the trend of longer summers. In most recent years, summer weather - and my unofficial definition of the season - has usually lasted into September.
There's data to back this up. Summers almost everywhere are longer than they were three decades ago, including here in Vermont.
"Climatologist Brian Brettschneider examined the hottest 90 days of the year from 1965 to 1994 and compared their frequency over 1995 to 2024. He found that the temperature that used to kick off the hottest three months of the year expanded beyond the calendar definition of summer."
Brettschneider looked at a whole bunch of cities, including Burlington, Vermont. From 1965 to 1994, the hottest 90 days of summer - when the average temperature was 64 degrees or warmer - ran from June 6 to September 3 in Burlington.
From 1994 to 2004, the average length of summer - the time it was 64 degrees or warmer - increased by 13 days and ran from June 1 to September 11.
Climate change is lengthening our summers and making them hotter. Despite the cool end of this August, the summer of 2025 in Burlington is very likely to be among the top ten hottest on record.
There are actually 15 summers in Burlington's top ten warmest summer list due to ties. Not including this summer, eight of those top 15 hottest summers have occurred since 2005, and four of them have happened since 2020. So there's a real warming trend here.
Even though this summer is likely among the hottest on record in Vermont, it is turning into an exception to Brettschneider's longer summer trend.
You're always going to have exceptions to the rules. Even if those are new rules. Lately, a persistent weather pattern is bringing cool air from Canada.
Temperatures will continue below normal today through Sunday, then they should rise to near or slightly above normal most of next week. After that, trends indicate another big cool spell starting about a week from today.
Despite that, who knows? Summer could unexpectedly come roaring back. Under our climate changed weather patterns, weird surprises happen.
For instance, in 2017, summer seemed definitely over in late August and early September with consistently cool weather, with even some frost in the cold hollows on September 2. Then, from September 24 to 27, Burlington had an unprecedented four days in a row with temperatures reaching 90 degrees, by far the latest in the season 90 degree temperatures on record.
Given the track record of recent warm autumn, we might do something weird like that this year.
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