Frost Dates for 15237 — Pittsburgh, Pennsylvania

Half of springs at Emsworth L/D Ohio Rvr, PA see their last 32°F night by April 24; only one in ten is past it by April 9, and one in ten still has one after May 11. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 5 20%, and after May 11 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 50% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 27 in half of years, as early as October 13 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 9 days later, around November 5; in spring the one-in-ten date for 28°F is April 26, 15 days before the 32°F one. The freeze-free season lasts 186 days in a typical year, longer than at 72% of the 176 Pennsylvania stations; it reaches 205 days one year in ten and falls short of 165 one year in ten. On average 107 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 11 days longer, to about May 5, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 10 and March 8.

July is the warmest month at Emsworth L/D Ohio Rvr, PA, averaging 85°F by day and 64°F at night; January is the coldest at 39°F and 21°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 28% of years.

Warmth for growing adds up to 3,337 growing degree days a year (base 50°F), more than at 81% of the 176 Pennsylvania stations. 34% of them (1,142) have built up by the end of June, and July adds the most, 759. Precipitation totals 38.3 inches a year, most in July (3.6") and least in February (2.8"); May to September bring 45% of it.

The nearest other station, Glenwillard Dashields L&D, PA, 9 miles west of Pittsburgh, has a last frost 16 days earlier (April 8), a first frost 12 days later (November 8), a season 26 days longer.

The first measurable snow (0.1 inch or more) in Pittsburgh usually arrives around December 19, and the last of the season around February 22. Those are the middle dates across the winters of 1991–2020 at Emsworth L/D Ohio Rvr, PA, 4.5 miles away: half of years saw snow earlier, half later. Snow fell in 79% of those winters. The last 32°F night of spring typically comes 61 days after the last snow.

ZIP 15237 is 5 miles from Emsworth L/D Ohio Rvr, PA, which stands at 717 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 18 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 15237 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.