Frost Dates for 63090 — Washington, Missouri

Half of springs at Washington, MO see their last 32°F night by April 8; only one in ten is past it by March 24, and one in ten still has one after April 22. Planting tender crops after April 13 leaves a 30% risk of a frost on them, after April 17 20%, and after April 22 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 25 in half of years, as early as October 13 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 4; in spring the one-in-ten date for 28°F is April 11, 11 days before the 32°F one. The freeze-free season lasts 199 days in a typical year, longer than at 64% of the 158 Missouri stations; it reaches 220 days one year in ten and falls short of 180 one year in ten. On average 116 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 20, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 9 and March 1.

July is the warmest month at Washington, MO, averaging 88°F by day and 67°F at night; January is the coldest at 40°F and 20°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 3,948 growing degree days a year (base 50°F), fewer than at 59% of the 158 Missouri stations. 37% of them (1,467) have built up by the end of June, and July adds the most, 857. Precipitation totals 44.2 inches a year, most in May (5.3") and least in January (2.5"); May to September bring 48% of it.

The nearest other station, Union, MO, 6 miles south of Washington, has a last frost 3 days later (April 11), a first frost 2 days earlier (October 23), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Washington usually arrives around December 11, and the last of the season around February 15. Those are the middle dates across the winters of 1991–2020 at Washington, MO, 2.7 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 52 days after the last snow.

ZIP 63090 is 3 miles from Washington, MO, which stands at 487 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 63090 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.