FIRST ALERT: Sweltering Air to Return to New England Thursday

Heat index values will exceed 100 degrees for a number of communities Thursday

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For a day sitting on the cusp of record heat, New England is enjoying some fine weather Wednesday! 

Comfortable air owing to a reduced dew point – a lower measure of the amount of moisture in the air – means even inland high temperatures of 85 to 90 degrees will feel rather comfortable Wednesday afternoon. Meanwhile a sea breeze sets up from mid-morning onward at the coast, capping temperatures in the lower 80s for seaside communities with most of the day spent shy of 80 degrees in these spots. 

Deeper humidity and heat haven't been pushed far away – sitting just on the southern periphery of a small bubble of high pressure, or fair weather, chock full of comfortable air is the sweltering air that will be quick to return. 

In fact, overnight Wednesday night we’ll likely see areas of fog and low altitude clouds spreading north off the ocean into southern New England, particularly anywhere near the South Coast, making for a grey Thursday morning sky for some.

Within the first few hours of daylight, clouds will break for sunshine Thursday and this will start the meteoric temperature rise, propelling afternoon high temperatures into the 90s and near 100 degrees for some. Coupled with a dew point in the 60s representing moderately humid air, heat index values will exceed 100 degrees for a number of communities, prompting the continuance of our First Alert for impact to the body as we encourage keeping hydration and avoiding overexertion front of mind. 

Although scattered late day thunder is possible in the north country, for the most part there won’t be enough temperature contrast set up in the atmosphere to fire storms, though a very isolated strong late day storm can’t be ruled out in any given spot, although that’s unlikely. More likely is the development of thunderstorms Friday afternoon to evening as a slow-moving cold front approaches New England from the northwest, slow enough to give temperatures time to rebound into the 90s for many again with heat index values around 100 degrees in sweltering humidity. 

The highest chance for damaging storms later Friday will be in the northern half of New England, though a few strong storms can’t be ruled out in southern New England, either. The approaching cold front really slams the brakes on Saturday, stalling out and keeping the chance of scattered showers and thunder elevated, particularly in the afternoon, and giving southern New England cities like Boston a chance to clip 90 degrees. That would set up the three consecutive days needed for a heat wave. 

Regardless of how many communities record a heat wave, temperatures are expected to reach the middle 90s Sunday before another sluggish cold front arrives with scattered storms Monday and a more meaningful change in air that will lower temperatures a notch next week in our exclusive First Alert 10-day forecast.

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