Summer may end on a cooler note for parts of the U.S., with meteorologists suggesting that a weakened polar vortex could usher in below-average temperatures as September begins.

New York City broke a record Tuesday afternoon, hitting 100 degrees Fahrenheit at La Guardia Airport. Tampa, Florida, which ...

Thursday will bring cool temps more typical of October to Chicagoland, despite ample sunshine forecast for the metro area.

Parts of the South are facing temperatures as much as 20 degrees below normal this week as polar air descends on the U.S.

Extreme heat is impacting states across the country. See maps of high temperature forecasts and heat index levels.

US temperature, heat index map All of western New York could experience heat index values, or "feels like" temperatures, as high as 104 degrees Tuesday.