The National Weather Service issued a flood watch for Butler County and surrounding counties that is in effect until 10 p.m. tonight.

According to National Weather Service Pittsburgh, excessive rainfall of up to 2 inches in an hour could cause flash flooding while the watch is in effect. Runoff could flood rivers, creeks, streams and other flood-prone areas, as well as structures with poor drainage.

The flood watch also applies to Allegheny, Beaver, Mercer and Lawrence counties.

The service also said later forecasts could indicate whether it will issue a flash flood warning for the region.