Exactly one year ago, a derecho brought hurricane-force winds and sent trees toppling onto cars and homes. In Wallingford, one man was killed as downed power lines lit this home ablaze.
"Unprecedented wind storms came through the counties really without notice," said Delaware County Director Emergency Services Timothy Boyce.
The Delaware County Office of Emergency Management is tasked with responding to these situations.
"We'll see a sudden increase in calls everything from alarm systems, to more serious thugs like wires down, traffic accidents and flash floods," said Boyce.
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Susan Oh remembers the $60,000 in water damage left behind last summer at Bright Dry Cleaners in Darby.
"Oh my God, all of my store overflowed with water," said Oh.
Her small shop sits in a spot notorious for flooding: McDade Boulevard and Springfield Road.
Tropical Storm Isaias flooded Darby Creek last summer. On Thursday evening, Oh was once again worried about the flash flood watch and severe thunderstorm watch for the evening issued in our area.
"I'm very nervous. Today is going to be very heavy rain," said Oh.
RELATED: Tropical Storm Isaias floods Darby Borough, 2 children rescued from roof
Rain becomes a concern for emergency services as drivers try to navigate the waters.
"Every time we see people go in the water - they think it's two or three inches of water - then they get stuck and then there's a tragedy. Flash floods happen everywhere in our region," said Boyce.
Officials say now is a good time to check your emergency kit and talk to your family to make a plan of action, before you need one.