Frost Dates for 16153 — Stoneboro, Pennsylvania

Half of springs at Mercer, PA see their last 32°F night by May 15; only one in ten is past it by April 30, and one in ten still has one after June 1. Planting tender crops after May 23 leaves a 30% risk of a frost on them, after May 27 20%, and after June 1 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 3 in half of years, as early as September 19 one year in ten, and holds off past October 19 one year in ten. A hard freeze of 28°F follows 10 days later, around October 13; in spring the one-in-ten date for 28°F is May 21, 11 days before the 32°F one. The freeze-free season lasts 140 days in a typical year, shorter than at 94% of the 176 Pennsylvania stations; it reaches 163 days one year in ten and falls short of 117 one year in ten. On average 159 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 12 days longer, to about May 27, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 20 and April 1.

July is the warmest month at Mercer, PA, averaging 82°F by day and 56°F at night; January is the coldest at 35°F and 16°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 87% of years and June still brings one in 11% of years.

Warmth for growing adds up to 2,525 growing degree days a year (base 50°F), fewer than at 77% of the 176 Pennsylvania stations. 34% of them (848) have built up by the end of June, and July adds the most, 594.

The nearest other station, Franklin, PA, 14 miles east of Stoneboro and 205 feet lower, has a last frost 13 days earlier (May 2), a first frost 20 days later (October 23), a season 31 days longer.

The first measurable snow (0.1 inch or more) in Stoneboro usually arrives around November 19, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Mercer, PA, 10.8 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 42 days after the last snow.

ZIP 16153 is 11 miles from Mercer, PA, which stands at 1,220 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 16137 (Mercer). The 2023 USDA Plant Hardiness Zone Map lists ZIP 16153 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.