Philadelphia weather matched a record this spring, with the average temperature from March through May at 57.8 degrees Fahrenheit. That tied the spring of 1921 and gives residents a warmer baseline heading into June, July and August.
NOAA says the Philadelphia area temperature forecast for June, July and August is leaning above normal. Sarah Johnson, a warning coordination meteorologist at the National Weather Service in Mount Holly, New Jersey, said, “We have slightly better chances for above-normal temperatures,” but added, “That does not mean that you can’t have some cold periods in between.”
Philadelphia and 1921
The spring average matched the 1921 mark and ranked as tied for third-warmest on record. For people in Philadelphia, that does not translate into a single hot stretch so much as a season that already started from an elevated temperature base.
Since 1970, Philadelphia’s average spring and summer temperatures have each risen around 3 degrees Fahrenheit. Since 2020, the city has seen five of its 10 warmest years on record, and 2024 tied with 2012 as the warmest year on record after 2023 moved to third warmest.
Sarah Johnson on summer heat
Johnson’s forecast language points to a tilt, not a guarantee. The region has a better chance of running above normal, but the pattern can still break long enough for cold periods to interrupt the heat.
That is the part residents can use now: plan for a summer that leans warm, but do not assume every week will look the same. The practical adjustment is to prepare for heat during the season and watch for short-lived cool spells rather than treating one record-tying spring as a fixed summer forecast.
Gabriel Vecchi and heat trends
Gabriel Vecchi, a professor in the Department of Geosciences at Princeton University, said spring warmth in the Philadelphia region was influenced by strong, high-pressure air over the Atlantic Ocean that brought tropical air northward into the mid-Atlantic region. He also said weather variations are more likely to push temperatures to records or near-records when the baseline is warmer because of human-caused climate change.
Muhammad Azhar Ehsan, a climate scientist at the Center for Climate Systems Research at Columbia University, said, “We see more heat and heat extremes due to that background trend, or climate change.” His point fits the local record: a warmer baseline makes an already hot season easier to push into record territory.
Vecchi said, “It’s this combination between these larger-” as he discussed the way longer-term warming and year-to-year weather can line up. For Philadelphia residents, the immediate takeaway is simple: the summer outlook leans hot, and the spring record shows the city is starting from a warmer place than it once did.
