Pittsburgh Now Under Excessive Heat Warning; Conditions Dangerous

PITTSBURGH, PA — The heat wave gripping Pittsburgh and Southwestern Pennsylvania now is officially dangerous.

The National Weather Service has issued an Excessive Heat Warning until 8 p.m. The warning replaces the Excessive Heat Watch that had been in effect since Monday.

The warning is in effect for Allegheny, Butler, Washington, Beaver, Fayette and Westmoreland counties.

What is the difference between the watch and the warning?

The weather service previously had predicted heat index values topping out at 105 degrees. The forecast now calls for heat index values as high as 110 degrees with the weather service warning "Prolonged dangerous hot conditions are likely. Heat related illnesses increase significantly during extreme heat and high humidity events."

To underscore the historic nature of this heat wave, the weather service noted that the current Pittsburgh forecast keeps overnight lows at 70 degrees or warmer. There has never been a six-day or greater run of lows that warm in June in the 154 years of weather record-keeping.