Frost Dates for 63664 — Potosi, Missouri

Half of springs at Potosi 4 SW, MO see their last 32°F night by April 11; only one in ten is past it by March 26, and one in ten still has one after April 30. Planting tender crops after April 19 leaves a 30% risk of a frost on them, after April 24 20%, and after April 30 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 92% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 28 in half of years, as early as October 14 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 7 days later, around November 4; in spring the one-in-ten date for 28°F is April 16, 14 days before the 32°F one. The freeze-free season lasts 198 days in a typical year, longer than at 60% of the 158 Missouri stations; it reaches 219 days one year in ten and falls short of 175 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 13 days longer, to about April 24, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 5 and March 5.

July is the warmest month at Potosi 4 SW, MO, averaging 86°F by day and 67°F at night; January is the coldest at 40°F and 21°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 77% of years.

Warmth for growing adds up to 3,879 growing degree days a year (base 50°F), fewer than at 70% of the 158 Missouri stations. 37% of them (1,428) have built up by the end of June, and July adds the most, 817. Precipitation totals 45.5 inches a year, most in May (5.3") and least in February (2.7"); May to September bring 46% of it.

The nearest other station, Farmington, MO, 26 miles east of Potosi and 205 feet lower, has a last frost 2 days later (April 13), a first frost 7 days earlier (October 21), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Potosi usually arrives around December 3, and the last of the season around March 2. Those are the middle dates across the winters of 1991–2020 at Potosi 4 SW, MO, 2 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 40 days after the last snow.

ZIP 63664 is 2 miles from Potosi 4 SW, MO, which stands at 1,105 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 63664 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.