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Stifling heat will continue until Thursday

Drink plenty of fluids, the heat is here to stay for a few more days. Matthew J Lee/Globe Staff

By Dave Epstein, The Boston Globe

June 28, 2021

2 minutes to read

Temperatures quickly approached and in some cases surpassed 90 degrees late Monday morning as the second heat wave of the season was underway. Heat Indices already were near 100 before noon. This dangerously hot weather will continue through Wednesday before temperatures start to slowly become less intense Thursday but especially for the upcoming weekend.

Heat index 105° take it easy it out there. pic.twitter.com/Jte1efyQH9

— Dave Epstein (@growingwisdom) June 28, 2021

Obviously, it’s been hot in New England before and heat waves are nothing new. However, it is instructive to look at how this latest round of heat, as well as what we’ve experienced so far this season, fits into a general trend.

As you know, the climate continues to slowly warm and this year, as long as my forecast is correct, we will have had the second-most 90-degree days — 11 — through the end of June. There were 12 such days in 1976 through the first six months of the year. June 2021 will likely end up as the warmest June on record.

Summer temperatures have been steadily warming compared to previous decades.

Our current heat wave is thanks to the Bermuda high pressure system that typically sets up camp in the Atlantic and pumps warm and humid air northward each summer. The strength of this high determines just how intense the heat will be and how long it will last. Some models forecast that this pattern will become more entrenched each summer in the coming decades.

Late on Wednesday, there will likely be some showers and storms locally. Some of these could be strong or even severe and we will need to monitor that situation. Then the Bermuda high will begin to lose some of its strength Thursday, allowing temperatures to fall back to the 80s in the afternoon. By Friday morning, most of us should be in the 60s. Humidity levels also will drop late this week.

Wednesday likely brings a line of showers and thunderstorms, some of which could be strong to severe, in the afternoon just something to consider for planning purposes. pic.twitter.com/pTGWBLwOp0

— Dave Epstein (@growingwisdom) June 28, 2021

The holiday weekend is still a bit of a hot question mark. Some of the models keep clouds and precipitation into Saturday, while others clear us out with comfortably warm readings and moderate levels of humidity. It’s just too early to say with any confidence what’s going to happen. However, I can say that we’re not going to have any extreme heat over the weekend.

Looking deeper into the future, it does appear likely more 90-degree weather will arrive sometime the second week of July. The map below indicates New England in one of the higher chances of warmer than average readings in early to mid-July.