Frost Dates for 63565 — Unionville, Missouri

Half of springs at Unionville, MO see their last 32°F night by April 17; only one in ten is past it by April 4, and one in ten still has one after April 30. Planting tender crops after April 23 leaves a 30% risk of a frost on them, after April 26 20%, and after April 30 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 22 in half of years, as early as October 7 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 9 days later, around October 31; in spring the one-in-ten date for 28°F is April 22, 8 days before the 32°F one. The freeze-free season lasts 186 days in a typical year, shorter than at 77% of the 158 Missouri stations; it reaches 203 days one year in ten and falls short of 168 one year in ten. On average 134 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 11 days longer, to about April 28, and return around October 11. Severe cold of 16°F or below comes every winter, usually between November 24 and March 12.

July is the warmest month at Unionville, MO, averaging 86°F by day and 66°F at night; January is the coldest at 32°F and 15°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 3,365 growing degree days a year (base 50°F), fewer than at 98% of the 158 Missouri stations. 35% of them (1,172) have built up by the end of June, and July adds the most, 792. Precipitation totals 41.9 inches a year, most in May (6.0") and least in January (1.4"); May to September bring 60% of it.

The nearest other station, Green City 5N, MO, 9 miles south of Unionville, has a last frost 9 days later (April 26), a first frost 8 days earlier (October 14), a season 17 days shorter.

The first measurable snow (0.1 inch or more) in Unionville usually arrives around November 30, and the last of the season around March 23. Those are the middle dates across the winters of 1991–2020 at Unionville, MO, 1.6 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 25 days after the last snow.

ZIP 63565 is 2 miles from Unionville, MO, which stands at 1,060 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 63565 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.