Frost Dates for 24520 — Alton, Virginia

Half of springs at S Boston, VA see their last 32°F night by April 10; only one in ten is past it by March 25, and one in ten still has one after April 30. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 22 20%, and after April 30 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 84% of the 128 Virginia stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 30 in half of years, as early as October 17 one year in ten, and holds off past November 12 one year in ten. A hard freeze of 28°F follows 8 days later, around November 7; in spring the one-in-ten date for 28°F is April 13, 17 days before the 32°F one. The freeze-free season lasts 202 days in a typical year, longer than at 60% of the 128 Virginia stations; it reaches 220 days one year in ten and falls short of 179 one year in ten. On average 108 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 13 days longer, to about April 23, and return around October 22. Severe cold of 16°F or below comes in 96% of winters, usually between December 31 and February 12.

July is the warmest month at S Boston, VA, averaging 90°F by day and 67°F at night; January is the coldest at 51°F and 27°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 74% of years.

Warmth for growing adds up to 4,377 growing degree days a year (base 50°F), more than at 77% of the 128 Virginia stations. 37% of them (1,610) have built up by the end of June, and July adds the most, 890. Precipitation totals 46.5 inches a year, most in June (4.9") and least in February (3.0"); May to September bring 47% of it.

The nearest other station, Danville Regional Airport, VA, 16 miles west of Alton and 242 feet higher, has the same 50% last-frost date, a first frost 2 days earlier (October 28), a season 2 days shorter.

The first measurable snow (0.1 inch or more) in Alton usually arrives around January 1, and the last of the season around February 22. Those are the middle dates across the winters of 1991–2020 at Yanceyville 4 SE, NC, 17 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 47 days after the last snow.

ZIP 24520 is 13 miles from S Boston, VA, which stands at 329 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 24592 (South Boston). The 2023 USDA Plant Hardiness Zone Map lists ZIP 24520 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.