Frost Dates for 66002 — Atchison, Kansas

Half of springs at Atchison, KS see their last 32°F night by April 11; only one in ten is past it by March 29, and one in ten still has one after April 23. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 19 20%, and after April 23 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 89% of the 110 Kansas 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 15 one year in ten, and holds off past November 10 one year in ten. A hard freeze of 28°F follows 7 days later, around November 5; in spring the one-in-ten date for 28°F is April 14, 9 days before the 32°F one. The freeze-free season lasts 199 days in a typical year, longer than at 79% of the 110 Kansas stations; it reaches 219 days one year in ten and falls short of 179 one year in ten. On average 107 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 10 days longer, to about April 21, and return around October 20. Severe cold of 16°F or below comes every winter, usually between December 2 and March 4.

July is the warmest month at Atchison, KS, averaging 88°F by day and 69°F at night; January is the coldest at 36°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 85% of years.

Warmth for growing adds up to 4,006 growing degree days a year (base 50°F), fewer than at 66% of the 110 Kansas stations. 36% of them (1,451) have built up by the end of June, and July adds the most, 882. Precipitation totals 36.4 inches a year, most in May (5.3") and least in January (0.9"); May to September bring 62% of it.

The nearest other station, St Joseph Rosecrans Airport, MO, 19 miles northeast of Atchison, has a last frost 8 days later (April 19), a first frost 12 days earlier (October 17), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Atchison usually arrives around December 2, and the last of the season around March 8. Those are the middle dates across the winters of 1991–2020 at Atchison, KS, 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 34 days after the last snow.

ZIP 66002 is 2 miles from Atchison, KS, which stands at 945 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 66002 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.