Most of Massachusetts is under a heat advisory through Wednesday, and forecasters are urging residents to look out for the high temperatures.

Tuesday is shaping up to be our hottest day of the week. Thermometers will climb into the mid to upper 90s in the afternoon. When factoring in humidity, it’ll feel right at or above 100 degrees.

With this week's heat wave likely leaving conditions feeling like it is more than 100 degrees on Tuesday, Massachusetts could see another big change to the forecast before the week ends.

The affected areas include much of the southeastern coast, the midwest, the eastern US corridor stretching from Boston to Washington, DC and even parts of the Northeast and South. Meanwhile other parts of the country remained under a severe thunderstorm excessive rain watch on Monday.

The Storms Prediction Center has placed portions of our entire area in a "slight" risk, or level 2. The SPC also has increased the risk of some damaging, straight-line winds Friday afternoon and evening, particularly from Worcester County and areas south-westward.

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.

A heat advisory is in effect in Boston and several other Massachusetts communities through 7 p.m. on July 17. The National Weather Service warned of "dangerous heat and humidity" with heat indices soaring to 95 to 100 degrees. Boston Mayor Michelle Wu also declared a heat emergency for the City of Boston from July 16 to 18.

Boston faces rain and a thunderstorm Sunday, a 70% chance of precipitation, and an upcoming heatwave with highs near 80 degrees.

Heat advisories are in effect from Monday to Wednesday across the Northeast, the National Weather Service said.

As another bout of sweltering heat is set to hit Massachusetts, the MBTA is alerting riders that the extreme heat could cause delays on the commuter rail on Friday.