Frost Dates for 19140 — Philadelphia, Pennsylvania

Half of springs at Phila Franklin Inst, PA see their last 32°F night by March 30; only one in ten is past it by March 15, and one in ten still has one after April 12. Planting tender crops after April 4 leaves a 30% risk of a frost on them, after April 7 20%, and after April 12 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 94% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 17 in half of years, as early as November 4 one year in ten, and holds off past December 4 one year in ten. A hard freeze of 28°F follows 12 days later, around November 29; in spring the one-in-ten date for 28°F is March 31, 12 days before the 32°F one. The freeze-free season lasts 232 days in a typical year, the longest of the 176 Pennsylvania stations; it reaches 255 days one year in ten and falls short of 214 one year in ten. On average 62 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 9 days longer, to about April 8, and return around November 5. Severe cold of 16°F or below comes in 95% of winters, usually between January 9 and February 9.

July is the warmest month at Phila Franklin Inst, PA, averaging 89°F by day and 71°F at night; January is the coldest at 42°F and 28°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 44% of years.

Warmth for growing adds up to 4,429 growing degree days a year (base 50°F), the most of the 176 Pennsylvania stations. 35% of them (1,552) have built up by the end of June, and July adds the most, 941. Precipitation totals 50.9 inches a year, most in August (5.0") and least in February (3.3"); May to September bring 46% of it.

The nearest other station, Pennsauken 1N, NJ, 7 miles southeast of Philadelphia, has a last frost 16 days later (April 15), a first frost 17 days earlier (October 31), a season 33 days shorter.

The first measurable snow (0.1 inch or more) in Philadelphia usually arrives around December 20, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Phila Franklin Inst, PA, 4 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 24 days after the last snow.

ZIP 19140 is 4 miles from Phila Franklin Inst, PA, which stands at 60 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 44 other ZIP codes share the station; its figures are presented in full for 19120 (Philadelphia). The 2023 USDA Plant Hardiness Zone Map lists ZIP 19140 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.