Frost Dates for 81639 — Hayden, Colorado

Half of springs at Hayden, CO see their last 32°F night by June 1; only one in ten is past it by May 15, and one in ten still has one after June 16. Planting tender crops after June 7 leaves a 30% risk of a frost on them, after June 11 20%, and after June 16 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 September 20 in half of years, as early as September 7 one year in ten, and holds off past September 30 one year in ten. A hard freeze of 28°F follows 9 days later, around September 29; in spring the one-in-ten date for 28°F is June 1, 15 days before the 32°F one. The freeze-free season lasts 109 days in a typical year, shorter than at 79% of the 110 Colorado stations; it reaches 129 days one year in ten and falls short of 88 one year in ten. On average 197 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 16 days longer, to about June 17, and return around September 10. Severe cold of 16°F or below comes every winter, usually between October 30 and April 2.

July is the warmest month at Hayden, CO, averaging 86°F by day and 50°F at night; January is the coldest at 30°F and 8°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 50% of years.

Warmth for growing adds up to 1,831 growing degree days a year (base 50°F), fewer than at 68% of the 110 Colorado stations. 27% of them (491) have built up by the end of June, and July adds the most, 552. Precipitation totals 18.6 inches a year, most in April (2.2") and least in June (1.1"); May to September bring 38% of it.

The nearest other station, Craig Moffat Co Airport, CO, 14 miles west of Hayden and 281 feet lower, has a last frost 5 days later (June 6), a first frost 8 days earlier (September 12), a season 13 days shorter.

The first measurable snow (0.1 inch or more) in Hayden usually arrives around October 17, and the last of the season around May 9. Those are the middle dates across the winters of 1991–2020 at Hayden, CO, 0.4 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 23 days after the last snow.

ZIP 81639 is under a mile from Hayden, CO, which stands at 6,467 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 81639 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.