Frost Dates for 81425 — Olathe, Colorado

Half of springs at Montrose Regional Airport, CO see their last 32°F night by May 2; only one in ten is past it by April 19, and one in ten still has one after May 17. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 13 20%, and after May 17 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 56% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 8 in half of years, as early as September 26 one year in ten, and holds off past October 22 one year in ten. A hard freeze of 28°F follows 12 days later, around October 20; in spring the one-in-ten date for 28°F is May 5, 12 days before the 32°F one. The freeze-free season lasts 157 days in a typical year, longer than at 75% of the 110 Colorado stations; it reaches 177 days one year in ten and falls short of 137 one year in ten. On average 156 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 15 days longer, to about May 17, and return around September 30. Severe cold of 16°F or below comes every winter, usually between November 18 and March 5.

July is the warmest month at Montrose Regional Airport, CO, averaging 90°F by day and 58°F at night; January is the coldest at 39°F and 16°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 56% of years.

Warmth for growing adds up to 2,862 growing degree days a year (base 50°F), more than at 72% of the 110 Colorado stations. 33% of them (937) have built up by the end of June, and July adds the most, 744. Precipitation totals 8.4 inches a year, most in September (1.2") and least in January (0.4"); May to September bring 49% of it.

The nearest other station, Delta 3E, CO, 10 miles north of Olathe and 732 feet lower, has a last frost 1 day earlier (May 1), a first frost 1 day earlier (October 7), a season 2 days longer.

The first measurable snow (0.1 inch or more) in Olathe usually arrives around November 11, and the last of the season around April 18. Those are the middle dates across the winters of 1991–2020 at Montrose 4.0 NW, CO, 7.3 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 14 days after the last snow.

ZIP 81425 is 9 miles from Montrose Regional Airport, CO, which stands at 5,759 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 81425 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.