Frost Dates for 64644 — Hamilton, Missouri

Half of springs at Hamilton 2W, MO see their last 32°F night by April 23; only one in ten is past it by April 9, and one in ten still has one after May 6. Planting tender crops after April 29 leaves a 30% risk of a frost on them, after May 2 20%, and after May 6 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 94% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 17 in half of years, as early as October 2 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 9 days later, around October 26; in spring the one-in-ten date for 28°F is April 26, 10 days before the 32°F one. The freeze-free season lasts 175 days in a typical year, shorter than at 95% of the 158 Missouri stations; it reaches 195 days one year in ten and falls short of 157 one year in ten. On average 141 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 9 days longer, to about May 2, and return around October 7. Severe cold of 16°F or below comes every winter, usually between November 24 and March 12.

July is the warmest month at Hamilton 2W, MO, averaging 87°F by day and 66°F at night; January is the coldest at 35°F and 16°F. A freezing night is all but certain in every month from October 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 24% of years.

Warmth for growing adds up to 3,550 growing degree days a year (base 50°F), fewer than at 90% of the 158 Missouri stations. 35% of them (1,257) have built up by the end of June, and July adds the most, 818. Precipitation totals 40.1 inches a year, most in May (5.8") and least in January (1.1"); May to September bring 58% of it.

The nearest other station, Gallatin 1W, MO, 12 miles north of Hamilton, has a last frost 4 days earlier (April 19), a first frost 4 days later (October 21), a season 9 days longer.

The first measurable snow (0.1 inch or more) in Hamilton usually arrives around December 24, and the last of the season around February 19. Those are the middle dates across the winters of 1991–2020 at Hamilton 2W, MO, 2.5 miles away: half of years saw snow earlier, half later. Snow fell in 69% of those winters. The last 32°F night of spring typically comes 63 days after the last snow.

ZIP 64644 is 3 miles from Hamilton 2W, MO, which stands at 900 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 64644 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.