Frost Dates for 66021 — Edgerton, Kansas

Half of springs at Olathe Johnson Co Airport, KS see their last 32°F night by April 13; only one in ten is past it by March 30, and one in ten still has one after April 29. Planting tender crops after April 20 leaves a 30% risk of a frost on them, after April 23 20%, and after April 29 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 76% of the 110 Kansas stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 24 in half of years, as early as October 10 one year in ten, and holds off past November 4 one year in ten. A hard freeze of 28°F follows 9 days later, around November 2; in spring the one-in-ten date for 28°F is April 19, 10 days before the 32°F one. The freeze-free season lasts 193 days in a typical year, longer than at 66% of the 110 Kansas stations; it reaches 211 days one year in ten and falls short of 173 one year in ten. On average 110 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 23, and return around October 15. Severe cold of 16°F or below comes every winter, usually between November 30 and March 4.

July is the warmest month at Olathe Johnson Co Airport, KS, averaging 89°F by day and 68°F at night; January is the coldest at 39°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 86% of years.

Warmth for growing adds up to 4,091 growing degree days a year (base 50°F), fewer than at 51% of the 110 Kansas stations. 36% of them (1,488) have built up by the end of June, and July adds the most, 893. Precipitation totals 37.7 inches a year, most in June (5.3") and least in January (1.1"); May to September bring 59% of it.

The nearest other station, Hillsdale Lake, KS, 9 miles southeast of Edgerton, has a last frost 4 days earlier (April 9), a first frost 7 days later (October 31), a season 11 days longer.

The first measurable snow (0.1 inch or more) in Edgerton usually arrives around December 7, and the last of the season around February 28. Those are the middle dates across the winters of 1991–2020 at Paola, KS, 13.7 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 44 days after the last snow.

ZIP 66021 is 8 miles from Olathe Johnson Co Airport, KS, which stands at 1,087 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 66061 (Olathe). The 2023 USDA Plant Hardiness Zone Map lists ZIP 66021 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.