Philly weather: warm and wet summer likely ahead

This story is part of the WHYY News Climate Desk, bringing you news and solutions for our changing region.

From the Poconos to the Jersey Shore to the mouth of the Delaware Bay, what do you want to know about climate change? What would you like us to cover? Get in touch.

Temperatures in Philadelphia are expected to top 90 degrees on Thursday for the first time this season.

Forecasters say to expect a hot summer.

“It’s been warm the last couple years for sure,” said Mike Lee, a meteorologist in the National Weather Service forecast office in Mount Holly, New Jersey. “It’ll stay fairly warm.”

The National Weather Service predicts that southeastern Pennsylvania, Delaware and South Jersey will experience a warmer and wetter summer than normal.

“It certainly doesn’t mean that every single day is going to be a heatwave or every single day is going to be … 90, 100 degrees,” Lee said. “It’s more so that in terms of the overall weather patterns, it’s going to be favoring warmer days. So we could see more 90-degree days than we typically do over the summer season.”

This year’s first 90-degree day has come later in the season than usual, Lee said.

This summer’s above-normal forecast for temperature is more certain than the forecast for precipitation, said Sarah Johnson, another meteorologist at the Mount Holly forecast office.

“For precipitation, there isn’t quite as strong of a signal,” she said.

In 2023, El Niño drove record-high global temperatures. But since then, the El Niño–Southern Oscillation, which changes ocean temperatures in the Pacific, has shifted to La Niña and then neutral conditions. 

This summer, weather patterns are expected to bring moisture and warmth up from the Gulf to the Philadelphia region, Pennsylvania State Climatologist Kyle Imhoff said.

The forecast comes on top of rising temperatures due to climate change. According to the research by nonprofit Climate Central, average summer temperatures in Philadelphia have trended up by roughly 3 degrees since 1970. It’s too soon to say what role climate change may play in hot temperatures this summer, but the baseline has shifted, Imhoff said.

“We’re starting off already at an elevated level,” he said. “So if we’re saying warmer and wetter than typical, well, the typical has gotten warmer and wetter.”