Frost Dates for 80534 — Johnstown, Colorado

Half of springs at Loveland 2N, CO see their last 32°F night by May 10; only one in ten is past it by April 30, and one in ten still has one after May 22. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 18 20%, and after May 22 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 81% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 1 in half of years, as early as September 15 one year in ten, and holds off past October 13 one year in ten. A hard freeze of 28°F follows 9 days later, around October 10; in spring the one-in-ten date for 28°F is May 14, 8 days before the 32°F one. The freeze-free season lasts 142 days in a typical year, shorter than at 50% of the 110 Colorado stations; it reaches 157 days one year in ten and falls short of 124 one year in ten. On average 174 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 12 days longer, to about May 22, and return around September 22. Severe cold of 16°F or below comes every winter, usually between November 5 and March 29.

July is the warmest month at Loveland 2N, CO, averaging 89°F by day and 55°F at night; January is the coldest at 44°F and 13°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 88% of years.

Warmth for growing adds up to 2,510 growing degree days a year (base 50°F), more than at 51% of the 110 Colorado stations. 30% of them (762) have built up by the end of June, and July adds the most, 677. Precipitation totals 15.7 inches a year, most in May (2.7") and least in January (0.5"); May to September bring 54% of it.

The nearest other station, Greeley Unc, CO, 12 miles east of Johnstown and 365 feet lower, has a last frost 8 days earlier (May 2), a first frost 7 days later (October 8), a season 17 days longer.

The first measurable snow (0.1 inch or more) in Johnstown usually arrives around November 2, and the last of the season around April 29. Those are the middle dates across the winters of 1991–2020 at Greeley 5.2 SW, CO, 7.5 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 11 days after the last snow.

ZIP 80534 is 11 miles from Loveland 2N, CO, which stands at 5,080 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 80538 (Loveland). The 2023 USDA Plant Hardiness Zone Map lists ZIP 80534 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.