Frost Dates for 35143 — Shelby, Alabama

Half of springs at Thorsby Exp Stn, AL see their last 32°F night by March 21; only one in ten is past it by February 28, and one in ten still has one after April 10. Planting tender crops after March 30 leaves a 30% risk of a frost on them, after April 3 20%, and after April 10 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 70% of the 115 Alabama stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 11 in half of years, as early as October 29 one year in ten, and holds off past December 1 one year in ten. A hard freeze of 28°F follows 14 days later, around November 25; in spring the one-in-ten date for 28°F is March 26, 15 days before the 32°F one. The freeze-free season lasts 235 days in a typical year, longer than at 57% of the 115 Alabama stations; it reaches 263 days one year in ten and falls short of 209 one year in ten. On average 46 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 15 days longer, to about April 5, and return around November 1. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 66%.

July is the warmest month at Thorsby Exp Stn, AL, averaging 90°F by day and 69°F at night; January is the coldest at 55°F and 33°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 86% of years and April still brings one in 25% of years.

Warmth for growing adds up to 5,289 growing degree days a year (base 50°F), fewer than at 62% of the 115 Alabama stations. 40% of them (2,102) have built up by the end of June, and July adds the most, 907. Precipitation totals 56.3 inches a year, most in March (5.8") and least in October (2.9"); May to September bring 39% of it.

The nearest other station, Alabaster Shelby Co Airport, AL, 16 miles northwest of Shelby, has a last frost 9 days earlier (March 12), a first frost 5 days later (November 16), a season 13 days longer.

Measurable snow is rare here: only 2 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Thorsby Exp Stn, AL, 13.5 miles away, so there is no typical first-snow date to plan around.

ZIP 35143 is 14 miles from Thorsby Exp Stn, AL, which stands at 680 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 35085 (Jemison). The 2023 USDA Plant Hardiness Zone Map lists ZIP 35143 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.