Frost Dates for 63401 — Hannibal, Missouri

Half of springs at Hannibal Wtr Wks, MO see their last 32°F night by April 10; only one in ten is past it by March 28, and one in ten still has one after April 25. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 21 20%, and after April 25 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 54% of the 158 Missouri stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 27 in half of years, as early as October 14 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 9 days later, around November 5; in spring the one-in-ten date for 28°F is April 15, 10 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 217 days one year in ten and falls short of 180 one year in ten. On average 114 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 21, and return around October 18. Severe cold of 16°F or below comes every winter, usually between December 2 and March 5.

July is the warmest month at Hannibal Wtr Wks, MO, averaging 86°F by day and 67°F at night; January is the coldest at 35°F and 18°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 83% of years.

Warmth for growing adds up to 3,741 growing degree days a year (base 50°F), fewer than at 80% of the 158 Missouri stations. 36% of them (1,352) have built up by the end of June, and July adds the most, 821. Precipitation totals 41.3 inches a year, most in May (5.0") and least in January (2.1"); May to September bring 52% of it.

The nearest other station, Saverton L&D 22, MO, 9 miles southeast of Hannibal and 240 feet lower, has a last frost 6 days earlier (April 4), a first frost 8 days later (November 4), a season 13 days longer.

The first measurable snow (0.1 inch or more) in Hannibal usually arrives around December 5, and the last of the season around March 11. Those are the middle dates across the winters of 1991–2020 at Hannibal Wtr Wks, MO, 2.3 miles away: half of years saw snow earlier, half later. Snow fell in 92% of those winters. The last 32°F night of spring typically comes 30 days after the last snow.

ZIP 63401 is 2 miles from Hannibal Wtr Wks, MO, which stands at 712 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 63401 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.