The autumnal equinox begins Monday, which means the upcoming weekend is our final weekend of astronomical summer. This time of the year can feature a big whiplash in temperatures, and we are going to see quite the swing between Wednesday and the weekend.
After some potential frosty weather over the next two days, the temperatures should start to rise as we hit Friday afternoon. I expect the weather to feel like summer this weekend with many areas reaching or exceeding 80 degrees.
If you take a look at temperatures just before sunrise Thursday, some of the models are predicting readings in the upper 20s in the very coldest spots of New England — interior Maine and parts of Northern Worcester and Franklin counties. We could see a frost advisory for some locations. Those of you susceptible to early frosts should plan to cover plants up Wednesday night.
By the time we get to Saturday and Sunday, readings should be well into the 70s and even the low and mid-80s. Some locations could see a 50-degree swing in temperatures during this time.
Early autumn heat is not unusual, but we haven’t seen any extreme heat — meaning temperatures in the upper 80s or even 90s — in late September and October for quite a while.
We know that over the past several decades temperatures have warmed up, but what is interesting is that the absolute extreme highest temperatures in fall have not really changed. You might be surprised that our warmest temperatures after Sept. 20 mostly occurred prior to the year 2000. Of the top 20 warmest days in late September and early October, only one has occurred this century.
Don’t take this as proof that there isn’t climate change, by the way. A warming and changing climate doesn’t do so evenly, and there are pockets where we see the change occurring differently or slowly.
In addition to the warm weather this weekend, we continue to look at very dry conditions, which should last through the rest of the month. We’ve had adequate precipitation this year, so we’re not really in danger of any sort of a major drought. If you are doing any fall planting or reseeding your lawn, rainfall is going to be at a premium for the next two weeks, so you’ll have to use irrigation in order to get things established.
It seems that we may turn cooler as we start October with below-average temperatures, but forecasts that far in the future don’t hold a lot of validity.
Follow Dave Epstein on Twitter @growingwisdom.