The National Weather Service has extended the heat advisory for parts of Hampden County through Wednesday evening, where the threat of heat illness will be the greatest due to the high humidity and hot temperatures.
Meteorologist Matthew Belk said a heat index value of 99 is expected.
"One of the reasons that we have the heat index is that we are trying to account for the effect of humidity on the body as well as the heat," he said.
Belk said forecasters calculate the heat index using a complex equation involving the projected heat and humidity. And as for why the heat advisory is just for eastern Hampden County, Belk said that has to do with the definition of heat index.
"While there may be a few spots in western Hampden County and up in Hampshire County that may have heat indexes of 95 degrees, it's not representative of the area at large," he said.
To counteract the heat, residents are encouraged to drink plenty of fluids, seek out air-conditioning, stay out of the sun, and check up on relatives and neighbors.
