A heat advisory goes into effect Thursday for parts of Connecticut where heat index values will soar past 100 degrees on Friday.

Temperatures will soar to the upper 80s and low 90s Thursday as dew points climb in many areas, making the air feel thick and heavy. A heat advisory is in effect through Friday.

The Pensacola area is under a heat advisory for the second day in a row. A cluster of showers and thunderstorms will offer relief on Wednesday.

A Heat Advisory remains in effect for most North Alabama and Middle Tennessee counties through 9:00 PM CDT as the heat index will range from 100 to 109 degrees today. Today is mostly sunny to partly cloudy with warm high temperatures in the middle 90s.

As the ridge of high pressure and dry air fully take hold on Saturday, rain chances plummet to 20%. Without widespread clouds and rain to cool things off in the afternoon, temperatures will rise into the low to mid-90s, with heat indices into the triple digits.

How is the heat index calculated, and why is it more important than the air temperature during some heat waves?

With heat index values expected to top 110 degrees, Knox County residents are urged to take precautions. Here's where to find cooling centers nearby.

Record-high minimum temperatures, in which temperatures don't drop in the nighttime hours, are likely across much of the U.S.