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My weather wishfulness is split this time of year. I want it to get cold so skiing will start, but I want it to stay warm so all those green tomatoes in my garden will ripen before frost.

This mental quandary led me to wonder how the date of our first frost is being affected as the climate warms and winters shrink in length. I figured it was getting later but perception is often wrong, so I asked the Northeast Regional Climate Center in Ithaca, N.Y., for data.

Surprise! There’s no obvious trend, as is shown by the poorly formatted chart at the top of this article. (Formatting is my error – Google Sheets is confusing.) It shows the date of first recorded frost at Concord Municipal Airport from 1981 (on the left) to 2019, when frost came on Oct. 5.

The average (mean) date is Sept. 27 and the range runs from Aug. 29 (wow!) in 1986 to Oct. 20 in 2005. Most of these days are just barely frosty, with low temperatures of 32 or 31 Fahrenheit.

I will add one proviso: Detecting patterns by eye is hard, and when you have a fairly small number of data points like this, changing the range can make a big difference. So this conclusion of mine should be taken with a big grain of salt.

By the way, the last frost of the season doesn’t show any pattern that I can see, either, although 2018’s record early item is startling:

Last frost of the winter at Concord, NH from 1981 (left) to 2019. Source: Northeast Regional Climate Center

This just goes to show that weather and climate are complicated. Lots of data show that our winters are getting less wintery (alas) but you don’t see it in this data point.

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