Frost Dates for 65791 — Thayer, Missouri

Half of springs at Mammoth Spring, AR see their last 32°F night by April 12; only one in ten is past it by March 27, and one in ten still has one after April 27. Planting tender crops after April 19 leaves a 30% risk of a frost on them, after April 23 20%, and after April 27 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 54% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 24 in half of years, as early as October 11 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 10 days later, around November 3; in spring the one-in-ten date for 28°F is April 16, 11 days before the 32°F one. The freeze-free season lasts 194 days in a typical year, shorter than at 50% of the 158 Missouri stations; it reaches 216 days one year in ten and falls short of 174 one year in ten. On average 103 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 24, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 8 and February 25.

July is the warmest month at Mammoth Spring, AR, averaging 90°F by day and 66°F at night; January is the coldest at 47°F and 23°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 80% of years.

Warmth for growing adds up to 4,294 growing degree days a year (base 50°F), more than at 80% of the 158 Missouri stations. 38% of them (1,614) have built up by the end of June, and July adds the most, 879. Precipitation totals 48.8 inches a year, most in May (5.3") and least in June (3.3"); May to September bring 40% of it.

The nearest other station, Alton, MO, 12 miles northeast of Thayer and 311 feet higher, has a last frost 5 days later (April 17), a first frost 3 days earlier (October 21), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Thayer usually arrives around January 22, and the last of the season around February 26. Those are the middle dates across the winters of 1991–2020 at Mammoth Spring, AR, 3.4 miles away: half of years saw snow earlier, half later. Snow fell in 63% of those winters. The last 32°F night of spring typically comes 45 days after the last snow.

ZIP 65791 is 3 miles from Mammoth Spring, AR, which stands at 502 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 65791 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.