Frost Dates for 37931 — Knoxville, Tennessee

Half of springs at Oak Ridge Asos, TN see their last 32°F night by March 31; only one in ten is past it by March 11, and one in ten still has one after April 15. Planting tender crops after April 5 leaves a 30% risk of a frost on them, after April 9 20%, and after April 15 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 78% of the 144 Tennessee stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 4 in half of years, as early as October 22 one year in ten, and holds off past November 18 one year in ten. A hard freeze of 28°F follows 11 days later, around November 15; in spring the one-in-ten date for 28°F is April 3, 12 days before the 32°F one. The freeze-free season lasts 218 days in a typical year, longer than at 87% of the 144 Tennessee stations; it reaches 241 days one year in ten and falls short of 198 one year in ten. On average 68 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 April 12, and return around October 27. Severe cold of 16°F or below comes in 90% of winters, usually between January 3 and February 1.

July is the warmest month at Oak Ridge Asos, TN, averaging 89°F by day and 69°F at night; January is the coldest at 48°F and 30°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 46% of years.

Warmth for growing adds up to 4,727 growing degree days a year (base 50°F), more than at 78% of the 144 Tennessee stations. 39% of them (1,839) have built up by the end of June, and July adds the most, 901. Precipitation totals 55.6 inches a year, most in February (5.6") and least in October (3.1"); May to September bring 39% of it.

The nearest other station, Oak Ridge Atdd, TN, 8 miles west of Knoxville, has a last frost 5 days later (April 5), a first frost 3 days earlier (November 1), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Knoxville usually arrives around January 6, and the last of the season around February 12. Those are the middle dates across the winters of 1991–2020 at Oak Ridge Atdd, TN, 7.5 miles away: half of years saw snow earlier, half later. Snow fell in 83% of those winters. The last 32°F night of spring typically comes 47 days after the last snow.

ZIP 37931 is 7 miles from Oak Ridge Asos, TN, which stands at 910 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 37931 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.