Storm Threats, Searing 105-Degree Heat Index Spark Emergencies Across MA: Latest Forecast

MASSACHUSETTS — A combination of extreme heat and tropical humidity could produce heat indexes of up to 105 degrees across Massachusetts on Wednesday and Thursday, according to the National Weather Service.

Boston Mayor Michelle Wu on Wednesday morning declared a heat emergency in that city, while a Heat Advisory issued across the region on Tuesday remains in effect through Thursday at 7 p.m. The Heat Advisory is in effect for most of Massachusetts, except for the Berkshires, portions of Cape Cod and the Islands.

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The high temperature forecast for Wednesday was 92 degrees with heat indexes reaching 95 to 105 degrees. There is a chance of a thunderstorm late in the afternoon.

Wednesday night will be a sultry one with low temperatures hovering in the mid- to upper-70s.

Thursday will likely be the third straight day of 90 degrees or higher temperatures, officially triggering the third heat wave of the season for much of Greater Boston. The high temperature is forecast as 90 degrees with a heat index of 97.

There is also an increased chance of thunderstorms after 2 p.m. on Thursday with some of those storms potentially severe.

Friday will bring some relief after a hot start as temperatures reach the late 80s before humidity falls off later in the day following the passage of a cold front.

That is setting the stage for a much more comfortable weekend with mostly sunny skies and a high of 82 on Saturday, followed by a chance of showers and a high of 81 on Sunday.

(Scott Souza is a Patch field editor covering Beverly, Danvers, Marblehead, Peabody, Salem and Swampscott. He can be reached at Scott.Souza@Patch.com. X/Twitter: @Scott_Souza.)

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