Frost Dates for 63301 — Saint Charles, Missouri

Half of springs at St Charles Elm Pt, MO see their last 32°F night by April 8; only one in ten is past it by March 23, and one in ten still has one after April 24. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 20 20%, and after April 24 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 35% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 29 in half of years, as early as October 16 one year in ten, and holds off past November 12 one year in ten. A hard freeze of 28°F follows 12 days later, around November 10; in spring the one-in-ten date for 28°F is April 15, 9 days before the 32°F one. The freeze-free season lasts 203 days in a typical year, longer than at 78% of the 158 Missouri stations; it reaches 225 days one year in ten and falls short of 183 one year in ten. On average 105 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 21, and return around October 19. Severe cold of 16°F or below comes every winter, usually between December 12 and February 28.

July is the warmest month at St Charles Elm Pt, MO, averaging 88°F by day and 68°F at night; January is the coldest at 40°F and 22°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 4,108 growing degree days a year (base 50°F), more than at 58% of the 158 Missouri stations. 37% of them (1,514) have built up by the end of June, and July adds the most, 873. Precipitation totals 45.8 inches a year, most in May (5.5") and least in January (2.7"); May to September bring 47% of it.

The nearest other station, St Peters 2 SE, MO, 5 miles southwest of Saint Charles, has a last frost 1 day later (April 9), a first frost 3 days earlier (October 26), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Saint Charles usually arrives around December 9, and the last of the season around February 24. Those are the middle dates across the winters of 1991–2020 at St Charles Elm Pt, MO, 0.5 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 43 days after the last snow.

ZIP 63301 is under a mile from St Charles Elm Pt, MO, which stands at 472 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 63301 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.