NWS: Severe Thunderstorm Watch Until 9 p.m. [Updated]

The National Weather Service has issued a Severe Thunderstorm Watch for Philadelphia and all surrounding counties through 9 p.m. Wednesday.

According to the NWS, conditions are favorable for thunderstorms containing 1-inch hail and the possibility of wind gusts of at least 58 mph.

Heavy rain and "dangerous" cloud-to-ground lightning are possible.

The American Red Cross of Southeastern Pennsylvania offered some sound advice for thunderstorms on its Twitter feed.

Some of it you've been hearing since you were in elementary school: for example, if you are stuck outside, avoid high ground, water, tall trees, and metal objects. Other tips, however, might not occur to everyone.

"Bring items in from outside NOW that could blow away during a storm," the agency said. Waiting until you see the sky darken and hear thunder rumbling can place you at risk for being struck by lightning.

The agency also asked people to evacuate mobile homes that can blow over in high winds and to stay indoors for at least 30 minutes after the last thunderclap is heard.

A chance of winds greater than 60 mph and up to two inches of rain were forecast for later Wednesday.