Weather
Philadelphia, PA Weather Oct. 11: Flash Flooding, Severe Storms Possible as Isaias Remnants Arrive
PHILADELPHIA, PA – Philadelphia, southern New Jersey and Delaware could face heavy thunderstorms, localized flash flooding and isolated severe weather Sunday, Oct. 11, as the remnants of Hurricane Isa
By Paige Sullivan · 2026-10-09T12:40:24.638Z
PHILADELPHIA, PA – Philadelphia, southern New Jersey and Delaware could face heavy thunderstorms, localized flash flooding and isolated severe weather Sunday, Oct. 11, as the remnants of Hurricane Isaias move into the region.
According to the National Weather Service in Philadelphia/Mount Holly, the system is expected to affect the area Sunday into Monday, bringing several weather hazards, although forecasters currently characterize the overall risks as marginal.
Heavy showers and thunderstorms Sunday and Sunday night could produce rainfall rates of 1 to 2 inches per hour in some locations.
The Weather Prediction Center has placed portions of southeastern Pennsylvania, southern New Jersey and Delaware under a Marginal Risk of excessive rainfall, Level 1 of 4, indicating at least a 5% chance of rainfall exceeding flash flood guidance within 25 miles of a point.
Forecasters emphasize that confidence in the flash flooding forecast remains low.
Severe thunderstorms are also possible Sunday afternoon and evening, with the greatest risk focused south of the Philadelphia metropolitan area.
The Storm Prediction Center identifies a Marginal Risk of severe weather, Level 1 of 5, across portions of southern New Jersey and Delaware.
Locally damaging winds and an isolated tornado are the primary severe weather concerns. The designation indicates isolated severe thunderstorms are possible, rather than a widespread severe weather outbreak.
Along the coast, minor tidal flooding is another concern during Sunday's and Monday's high tides.
The Weather Service identifies vulnerable locations along the New Jersey and Delaware coasts, Delaware Bay and the tidal Delaware River.
Minor flooding could affect traditionally flood prone roads and low lying coastal communities, including portions of the Jersey Shore and Delaware Bay shoreline.
Residents should monitor updated forecasts, particularly those in flood prone neighborhoods and coastal areas, and ensure they can receive weather watches and warnings.