Record May Heat Often (But Not Always!) Leads To Hot Summers

Watering the gardens in St. Albans, Vermont during a 
record heat wave in May, 2020.  I found a correlation
between record May heat and hot summers, but
that doesn't work every time. 

 Despite the patchy frost around this morning, things are still on track for possible near record high temperatures late in the week in Vermont. And at least if the past repeats itself, chances are we will have a hot summer, too. 

Heat and cold waves come and go, and usually they don't have much bearing on subsequent seasons. But I did find a correlation between heat waves in May and hot summers. 

Record May heat in 1911, 1944, 1975, 1977, 1979, 2017, 2020 and 2021 were followed by hot summers, or at least stretches of additional record heat in the subsequent summer.

In 1911, the hottest temperature on record for the state of Vermont occurred on July 4, 1911 with a reading of 105 degrees in Vernon.

The May, 1944 hot spell was followed by a reading of 101 degrees in August of that year, still the hottest day on record for Burlington. 

Record may heat in 1975 was followed by the hottest day on record for the New England region, when the temperature reached 107 degrees in New Bedford and Chester, Massachusetts.

Of course, there are exceptions to this hot May/hot summer trend.   For instance, it got into the 90s for a couple days in May, 1992 and the following summer was quite chilly. A heat wave in late May 1978 led to an average to slightly coolish summer. 

You'll notice from might list of May heat waves above that they are happening more frequently in recent years. A lot of that is  the effects of climate change takes hold. No matter what happens, the chances of a hot summer have increased anyway. The dice are loaded toward heat.

We can still have cool summers. We'll still get "air conditioned" Julys. They're just less likely than they used to be. 

For what it's worth, long range forecasts from NOAA's Climate Prediction Center predict a hotter than normal summer nationwide, especially in the Rocky Mountains and New England.  Do note that such long range forecasts, while useful, don't have the highest accuracy rate in the world. 

Also for what it's worth, I also found a bit of a connection between record chill in May and cool summers. Several bouts of May frost and freezes in 1961 led to a decidedly cool summer. 

May, 1966 featured several below freezing nights and the lowest May temperature on record in Burlington. Summer, 1966 was somewhat on the cool side, but not exceptionally cold.