Today is the last day of meteorological summer, and it’s been a long, boring three months. Save for a couple of tropical storms and a derecho or two, there weren’t many weather events that commanded attention. The big story has been the heat and humidity, and that’s what will continue through the first half of September.
Summer will slowly begin to wind down over the next month or two, but like winter, it’s hellbent on going out with a fit that will make us sweat a little longer.
Average high temperatures take a steep dip between the first and last day of the month, with most major cities listed above seeing about a ten degree drop in their average high over the course of September. New York City’s average high is just 70°F on September 30, with cooler weather typical in the Midwest. Even Mobile down in Ala-freakin’-bama starts to cool off to bearable levels once October rolls around.
Out with the heat goes the humidity, and in just a couple of weeks, it should start feeling nice just about everywhere. We just have to slog through at least one more heat wave, which will hopefully be the last before cooler temperatures arrive for good.
The culprit is a big ridge in the jet stream across much of the northern United States and Canada, which is building in ahead of a sharp trough digging into parts of the Pacific Northwest and British Columbia. Ridges of high pressure foster calm, warm weather, and with low-level winds blowing from the south, this air will not only be warm, but it’ll be muggy, too.
(That trough over the Pacific Northwest, by the way, should keep the region cool and moist through the rest of the week. That should help firefighters control the wildfire situation a little bit.)
How warm is warm? It depends on your heat tolerance, I guess, but objectively it’s going to be much warmer than normal. Tomorrow’s forecast high in Washington D.C. will be around 93°F according to The Weather Channel, which is nine degrees warmer than average for September 1. The high in Minneapolis will be 88°F, which is a full eleven degrees above normal. This ick will stick around through at least the first week of the month before finally (and slowly) cooling down from north to south.
Here’s some data from this morning’s run of the GFS model, showing the temperature trend over the next two weeks. Don’t focus on the exact numbers here—this is just a model forecast, and predicting high and low temperatures requires forecaster experience and knowledge. This product exists to show you trends more than anything else.
If current model trends hold true, abnormally warm conditions will stick around in Minneapolis through this weekend before nature flips the atmospheric switch on the lee side of Labor Day and temperatures turn downright gorgeous. I keep using Minneapolis as an example here because it’s a bastion of those crisp, fall temperatures that we cool weather people love to imagine as we stick our heads in the freezer. (But I digress.)
It’ll take a little longer for the moderation to dip farther south. Here’s the same model trendcast for New York City:
...and Washington D.C....
...and Memphis, for a change of pace:
Just about everyone is tired of the heat and humidity, and we’re almost to the point where it’s cool enough to open the windows. Temperatures will fluctuate and storms will boom and fizzle, but fall will come soon enough. Before you know it, we’ll be changing the clocks back an hour for absolutely no reason whatsoever. That’s something to look forward to!