Weather
Philadelphia, PA Weather Oct. 17–21: Lows Fall to 39° Saturday
Philadelphia, PA – A sharp weekend cooldown will bring temperatures into the 30s around Philadelphia by Saturday night, following a stretch of unusually warm weather and a rainy Friday. Sunshine retur
By Grant Holloway · 2026-10-14T08:26:15.549Z
Philadelphia, PA – A sharp weekend cooldown will bring temperatures into the 30s around Philadelphia by Saturday night, following a stretch of unusually warm weather and a rainy Friday. Sunshine returns for the weekend, but the colder nighttime temperatures could draw attention from gardeners preparing for the autumn frost season.
According to the National Weather Service in Philadelphia, temperatures are expected to reach 79 degrees Friday before falling to a high of just 54 Saturday. Overnight temperatures could drop to around 39 degrees Saturday night, marking a substantial change from the warmth earlier in the week.
Rain Moves Out Before Weekend Chill Friday's weather will feature showers, with thunderstorms also possible after 5 p.m. The National Weather Service places the precipitation probability at 90%, with southwest winds of 10 to 15 mph and gusts reaching 30 mph.
Showers and possibly a thunderstorm could continue into Friday evening before conditions improve overnight.
By Saturday, sunshine returns, although daytime temperatures will struggle to reach the mid 50s. Mostly clear skies Saturday night will accompany the forecast low near 39 degrees.
The cooler conditions follow a broader national weather pattern highlighted by NOAA's Weather Prediction Center, which expects strong Canadian high pressure to bring substantially colder temperatures into portions of the central United States late this week.
That national outlook does not establish a freeze threat for Philadelphia, where the available local forecast keeps temperatures above freezing.
Frost Season Brings Added Attention to Overnight Temperatures The National Weather Service's New York office notes that frost can develop when temperatures fall into the mid 30s, particularly in rural locations, while freezing conditions become possible at 32 degrees or below.
Its regional frost and freeze program covers portions of New Jersey, New York and Connecticut, rather than Philadelphia. The guidance nevertheless illustrates why gardeners should monitor overnight temperatures as autumn progresses.
Philadelphia's forecast currently shows no freezing temperatures through Tuesday.
After Saturday's chill, daytime temperatures begin recovering Sunday, reaching the lower 60s before climbing into the upper 60s Tuesday.
Five Day Weather Outlook: Oct. 17–21 Temperatures below represent the National Weather Service forecast for Philadelphia, Pennsylvania. The supplied forecast extends through Tuesday, Oct. 20; Wednesday's forecast was not provided.
Saturday, Oct. 17: Sunny and cooler, with a high near 54°. Mostly clear overnight, with a low around 39°. Sunday, Oct. 18: Sunny and milder, with a high near 61°. Mostly clear overnight, with a low around 42°. Monday, Oct. 19: Sunny, with a high near 65°. Partly cloudy overnight, with a low around 48°. Tuesday, Oct. 20: Partly sunny, with a high near 68°. Overnight temperatures were not provided. Wednesday, Oct. 21: Forecast information was not available in the supplied NWS outlook.