‘Positively tropical’ heat, humidity expected across Mass. Tuesday with thunderstorm risk

It could feel as warm as 100 in parts of Massachusetts on Tuesday, as a sweltering heat wave lingers over the Bay State.

Boston, Worcester and Springfield are all expected to exceed 90 on Tuesday, with humidity driving heat index values up near 100. All three cities, and most of the rest of the state, are under a heat advisory that lasts until 8 p.m.

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors,” National Weather Service forecasters warned.

An area of low pressure is moving east toward New England Tuesday, just as the remnants of a post-tropical cyclone move east of Cape Cod. Those factors are expected to create a plume of “extremely moist air … making it feel positively tropical over much of [Southern New England] this afternoon.”

All that moisture in the air is expected to lead to thunderstorms in the afternoon, which in turn are expected to create a risk of flash floods, particularly in the southern half of the region. Forecasters indicated the areas most likely to be impacted are those along or south of the Massachusetts Turnpike.

To that end, a flood watch is in place for parts of the state, including Worcester and Springfield, from 2 p.m. to 2 a.m.

It’s those areas that could see 1 to 2 inches of rain in an hour if thunderstorms do form, forecasters said. Still, storms are not expected to be widespread.

The heat will largely break on Wednesday, with highs plummeting down to the high 70s in the eastern part of the state and the mid-80s in Western Massachusetts.

Some showers and thunderstorms are possible, but it won’t be a washout, forecasters said.

The chance for rain and storms continues throughout the week, particularly in the afternoon. But forecasters don’t expect any major storms.