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It looks like dry, hot weather will continue for the rest of summer

Beachgoers at at Good Harbor Beach in Gloucester.Craig F. Walker/Globe Staff/The Boston Globe

In spite of the fact you might have had to pull on a sweatshirt for a morning walk today, it’s been a very hot summer with very little rain, most acutely over the interior.

Let’s put that statement in some perspective and figure where we stand with 11 days left in meteorological summer. Just a reminder, for record purposes: Summer is considered June 1 to Aug. 31, the warmest three-month period of the year.

The summer of 2020 is ranking as one of the hottest from Providence to Hartford to Worcester and on up to Portland, Maine. Logan Airport, where Boston’s records are kept, also is experiencing a hot summer, but because of some sea breezes the actual record is not quite as hot.


The number 1 represents the warmest summer so far on record.NOAA/SERCC

Whether or not we finish in first, second, or fifth place doesn’t really tell the whole story. This summer is just a continuation of a string of hot summers this century. As a matter of fact, if you look at records you will find that the hottest summers on record have mostly taken place in the past decade. This is statistically significant as our records go all the way back to 1872.

Since 1872, most of the hottest summers have occurred in this century.NOAA

The average temperature is composed of the overnight low and the daytime high. The lows at night have warmed faster than the daytime highs due to the increase in moisture, which doesn’t allow it to get as cool even after sunset. Moist air just holds heat better. Therefore, as CO2 levels have increased, humidity levels have risen as well and we end up not getting as many cool nights in the summer. This results in big increases in the average temperature over time.

This doesn’t mean that we’re not having more days in the 90s ― we are — it’s just that the days are not warming quite as quickly as the nights. Notice in the chart above: eight of the top 10 warm summer night temperatures have occurred in the past 10 years. That is amazing.


In addition to the higher temperatures, you probably have noticed a lack of rain this summer. A quick walk around a city neighborhood or in the middle of the woods and you can find plants under stress, with leaves drooping or completely falling off due to the lack of meaningful rainfall. Since the middle of May, we really have had significantly less precipitation than usual and are in an official drought. While there have been a few showers over the past couple of days, they have done little to alleviate the deficit of over 7 inches of precipitation this year. The only wet month we’ve had is April.

While it’s been a dry summer everywhere compared to average, it’s been very dry away from the coastline.NOAA/SERCC

Our last really dry summer was 2016 and we are not quite as dry as that if we don’t get rain again for the rest of the month, which is not impossible. This summer would rank as the 12th driest, and the driest since 2016, which was the driest summer on record.

With 11 days to go, the summer of 2020 ranks as the 11th driest on record. It can’t go any higher in the rankings, but could fall if there is any rain before Sept. 1.NOAA

Of course droughts and hot summers have occurred before. In the mid 1960s, a multiyear drought parched New England. The lower than average water years show up nicely on the long term charts.

Summer precipitation since 1950. Notice it can vary by more than 10 inches in one year.NOAA

What’s different about dry weather today versus five decades ago is that it’s consistently warmer, so the stress is there for greater humidity under higher temperatures. It would be interesting to study the two variables of heat and humidity over the past 20 years and how this impacts horticulture.


So what do the final days of summer hold as we get close to September? A quick glance at the models has temperatures well into the 80s and a smattering of 90s. Basically, a continuation of the pattern after this cooler interruption.

Temperatures are forecast by the GFS model to be quite warm to hot through the end of the month.WeatherBell

Rainfall also is forecast to be quite limited the rest of August. Fall is a great time to plant, but if you are planning on putting in anything from a new lawn to new trees and shrubs, just be prepared to need to water and with many towns having water bans in effect, this might be an issue. The dry weather is likely to affect the fall foliage, with leaves dropping earlier than usual and perhaps not exhibiting the brilliant color we sometimes observe.

Follow Dave Epstein @growingwisdom.