Heat and a chance of thunderstorms will be the defining characteristics of weather in Butler County in the coming days, according to the National Weather Service in Pittsburgh.

The office is predicting that temperatures will reach the low 90s today, Saturday and Sunday, with a peak of 92 degrees on Sunday. The one exception is Friday, when thunderstorms may roll into the area and will keep temperatures just below the 90 degree threshold, according to the office.

Next week should begin with slightly cooler temperatures, with Monday’s high expected to be 87 degrees.

Areas to the west and north of Butler County are expected to be hit with severe thunderstorms and high heat indexes, with high humidity limiting nighttime relief, the office predicts. Those conditions could affect northwestern Pennsylvania and eastern Ohio.