A dangerous heat dome is forecast to engulf much of the Eastern United States, with Boston at risk of reaching 100°F (38°C) next week — a rare and potentially historic event.
Extreme heat watch in effect from Sunday through Tuesday
A massive dome of high pressure, or “heat dome,” is projected to expand across the East Coast, sending temperatures soaring across Massachusetts. This weather phenomenon will trap hot air over the region, resulting in oppressive heat and little to no relief overnight.
The National Weather Service has issued an extreme heat watch effective from Sunday morning through Tuesday evening for much of eastern and central Massachusetts, including Suffolk, Plymouth, Bristol, Norfolk, Middlesex, Essex, Worcester, Franklin, Hampshire, and Hampden Counties.
Boston could hit 100°F — a rare milestone
Monday and Tuesday appear to be the most intense of the upcoming heat event. Forecast models show daytime highs pushing into the upper 90s°F (35–37°C), with a real possibility of touching 100°F (38°C) in Boston and surrounding suburbs by Tuesday afternoon.
If Boston hits the century mark, it would be only the 28th time on record and the first since 2022. It would also tie the all-time June high, last reached in 2021. The current record for June 25 stands at 95°F (35°C), set in 2013 — and forecasters expect it to be broken.
Heat wave timing coincides with solstice and strongest sun angle
This heat wave is arriving just as summer officially begins, with the solstice occurring at 10:42 p.m. on Friday. These are New England’s longest days of the year, and the sun is at its highest angle, meaning the UV index and solar heating are at their peak. That combination amplifies the intensity of this upcoming heat event.
While some areas may remain just below 90°F (32°C) on Sunday, others will already begin the climb. Wednesday is currently forecast to top out in the mid-80s°F (29–30°C), but that is subject to change as the weather pattern evolves.
Record-challenging heat likely in suburbs and rural towns
Areas outside Boston, including interior towns in Middlesex, Worcester, and Hampden Counties, may see even higher temperatures than the coast. Local conditions, including urban heat retention and lack of coastal breeze, could cause heat indices to climb well over 100°F (38°C), creating dangerous conditions especially in areas without adequate shade or cooling infrastructure.
Brief relief possible later in the week
A pattern shift may bring some cooling by late next week, along with the potential for isolated thunderstorms. However, until then, oppressive heat and humidity are expected to dominate the forecast across Massachusetts.
Stay alert to heat-related warnings, especially in Boston and other densely populated areas where the urban heat island effect can make nights just as unbearable as the daytime.
