The National Weather Service in Pittsburgh has issued a severe flash flood warning for northeastern Allegheny County and northwestern Westmoreland County until 4:30 p.m.
Allegheny County also is under a severe thunderstorm warning until 5:45 p.m.
More than an inch of rain could fall in less than 30 minutes, the National Weather Service said.
A heavy rain storm delayed the game between the Pittsburgh Pirates and Milwaukee Brewers at PNC Park about 2 p.m. The game resumed about 4:25 p.m.
National Weather Service meteorologist Lee Hendricks said thunderstorms are expected today across Eastern Ohio, the northern panhandle of West Virginia and Western Pennsylvania, and more thunderstorms are possible this evening.
"There is a lot of instability out there right now," he said.
Earlier this afternoon, storm warnings had been issued for Armnstrong and Butler counties.
National Weather Service meteorologist Bob Coblentz said today's storms brought heavy rain but very little wind, adding that there haven't been reports of damage. Any downed trees were likely caused by the ground being saturated and weak roots, not wind, he said.
"There's not a whole lot of wind associated with these storms," he said. "Just a lot of heavy rain."
He said while it might seem like a lot of rain, it's not unusual for this time of year, adding that there's a chance of thunderstorms every day through the Fourth of July.
"It's really a nuisance," Mr. Coblentz said.
Annie Siebert: email@example.com, 412-263-1613 or on Twitter @AnnieSiebert. First Published June 30, 2013 5:15 PM