Frost Dates for 18077 — Riegelsville, Pennsylvania

Half of springs at Springtown 1 NNE, PA see their last 32°F night by April 21; only one in ten is past it by April 8, and one in ten still has one after May 6. Planting tender crops after April 27 leaves a 30% risk of a frost on them, after May 1 20%, and after May 6 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 72% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 22 in half of years, as early as October 7 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 12 days later, around November 3; in spring the one-in-ten date for 28°F is April 23, 13 days before the 32°F one. The freeze-free season lasts 184 days in a typical year, longer than at 68% of the 176 Pennsylvania stations; it reaches 205 days one year in ten and falls short of 163 one year in ten. On average 122 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 2, and return around October 10. Severe cold of 16°F or below comes every winter, usually between December 7 and March 11.

July is the warmest month at Springtown 1 NNE, PA, averaging 83°F by day and 62°F at night; January is the coldest at 37°F and 19°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 22% of years.

Warmth for growing adds up to 2,932 growing degree days a year (base 50°F), fewer than at 52% of the 176 Pennsylvania stations. 33% of them (960) have built up by the end of June, and July adds the most, 707. Precipitation totals 53.3 inches a year, most in July (5.6") and least in February (3.2"); May to September bring 46% of it.

The nearest other station, Bucksville, PA, 5 miles south of Riegelsville and 473 feet lower, has a last frost 8 days later (April 29), a first frost 6 days earlier (October 16), a season 14 days shorter.

The first measurable snow (0.1 inch or more) in Riegelsville usually arrives around November 28, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Springtown 1 NNE, PA, 3 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 19 days after the last snow.

ZIP 18077 is 3 miles from Springtown 1 NNE, PA, which stands at 860 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 18036 (Coopersburg). The 2023 USDA Plant Hardiness Zone Map lists ZIP 18077 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.