Frost Dates for 80452 — Idaho Springs, Colorado

Half of springs at Georgetown, CO see their last 32°F night by May 30; only one in ten is past it by May 17, and one in ten still has one after June 14. Planting tender crops after June 5 leaves a 30% risk of a frost on them, after June 9 20%, and after June 14 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 19 in half of years, as early as September 5 one year in ten, and holds off past September 30 one year in ten. A hard freeze of 28°F follows 11 days later, around September 30; in spring the one-in-ten date for 28°F is May 31, 14 days before the 32°F one. The freeze-free season lasts 112 days in a typical year, shorter than at 75% of the 110 Colorado stations; it reaches 131 days one year in ten and falls short of 91 one year in ten. On average 210 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 June 14, and return around September 8. Severe cold of 16°F or below comes every winter, usually between November 1 and April 14.

July is the warmest month at Georgetown, CO, averaging 77°F by day and 49°F at night; December is the coldest at 36°F and 15°F. A freezing night is all but certain in every month from October 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 46% of years.

Warmth for growing adds up to 1,197 growing degree days a year (base 50°F), fewer than at 85% of the 110 Colorado stations. 24% of them (288) have built up by the end of June, and July adds the most, 402. Precipitation totals 18.3 inches a year, most in July (2.5") and least in January (0.8"); May to September bring 54% of it.

The nearest other station, Cabin Creek, CO, 10 miles southwest of Idaho Springs and 1,500 feet higher, has a last frost 7 days later (June 6), the same first-frost date, a season 9 days shorter.

The first measurable snow (0.1 inch or more) in Idaho Springs usually arrives around October 5, and the last of the season around May 19. Those are the middle dates across the winters of 1991–2020 at Georgetown, CO, 7.7 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 11 days after the last snow.

ZIP 80452 is 8 miles from Georgetown, CO, which stands at 8,520 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 80452 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.