The National Weather Service issued a Severe Thunderstorm Watch until 2:00 a.m. Monday for the following Pennsylvania counties: Berks, Bucks, Lehigh, Carbon, Monroe, Lancaster, Montgomery, Chester and Northampton.
"We are heading into a stormy pattern. Different areas will see different things," said NBC10 First Alert Weather meteorologist Brittney Shipp.
Storms began north and west of Philadelphia starting Sunday evening.
The strongest storms will be seen in the Poconos area overnight, according to Shipp. The areas under the watch can expect heavy downpours, frequent lightning, gusty winds and hail is possible.
Hail and flooding was reported in Chester County, according to the NWS.
Along the I-95 corridor, the chance for pop up thunderstorms continues overnight.
The thunderstorms will linger Monday with precipitation likely in the morning hours and again in the afternoon. There will be light rain starting at 5 a.m.
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A cold front is on its way resulting in cooler temperatures Tuesday.
The NBC10 First Alert Weather team is tracking the weather changes and updated details will be posted here.