Short heat wave moves into the region

Summer is finally here — unofficially, anyway — and after days of scattered showers across the Pittsburgh region, Pirates fans and Three Rivers Arts Festivalgoers won’t have to worry about an umbrella for the weekend.

Summertime heat? That’s something else.

Heat will move in starting Saturday and hang on for at least a few more days before moderating. The National Weather Service in Moon said to expect highs in the mid- to upper 80s and lows dipping only into the mid-60s at night.

According to weather service meteorologist Jason Frazier, the weekend’s heat will trend well above the average high temperatures of about 77 degrees. The temps shouldn’t approach recordbreaking highs.

“There’s potential for it to be even warmer, but there has been some change in how the pattern is going to be set up,” Mr. Frazier said. “The change is that we’re going to have high pressure move a little bit more to the east of us rather than being centered over us. What that’s going to allow for to happen is more moisture from the Gulf of Mexico is going to be drawn up, which would create more chances for showers and thunderstorms during the afternoon and early evening hours starting Monday.”

This weekend’s heat will also pose problems for those sensitive to poor air quality. The weather service has issued an air quality alert for Saturday for Allegheny and the surrounding counties; air pollution concentrations will mean those who are sensitive should avoid strenuous activity outdoors.

The humidity should be on the lower side for the weekend but will climb Monday. It will continue until Wednesday, when a new pattern is expected to settle in.

“We’re now in the summer, so we’re starting to see some of the summer temperatures’ heat, and we’re going to see more thunderstorms because of that,” Mr. Frazier said. “So just be on the lookout and be prepared.”