Mayor Michelle Wu declared a heat emergency for Boston from Wednesday through Friday, with the heat index predicted to fluctuate from 91 to 97 degrees with little overnight relief, the city announced.

Boston is in for a muggy humid, hot week, according to National Weather Service forecasts, with more flooding possible as the week goes on.

Flash floods hit cities and towns south of Boston Thursday as historic rain brought traffic to a crawl and shut down part of I-93.

Several Massachusetts communities south of Boston received as much as over 5 inches of rain, with flooding closing several streets and parts of Interstate 93.

A "considerable" flash flood warning was issued in Boston on Thursday morning as heavy rain pounded the city and areas to the south.Four to 6 inches of rain fell in the towns of Canton, Quincy and North Scituate.

An historic amount of rain fell in parts of Massachusetts Thursday, unleashing floods in towns south of Boston.

Communities south of Boston have seen as much as 4 and a half inches of rain, with a flash flood warning still in effect.

Boston, Quincy, Brockton, and other South Shore communities are under a flood watch until 9 a.m., according to the National Weather Service.

Boston's weather forecast includes sunny conditions, a heat wave, and chances of thunderstorms, with high humidity and advisories expected midweek.

With sweltering conditions bearing down on the city once again, Boston Mayor Michelle Wu has declared the city’s second heat emergency of the summer.