Frost Dates for 81647 — New Castle, Colorado

Half of springs at Rifle 3ENE, CO see their last 32°F night by May 23; only one in ten is past it by May 9, and one in ten still has one after June 6. Planting tender crops after May 30 leaves a 30% risk of a frost on them, after June 2 20%, and after June 6 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 45% of the 110 Colorado stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 25 in half of years, as early as September 13 one year in ten, and holds off past October 6 one year in ten. A hard freeze of 28°F follows 9 days later, around October 4; in spring the one-in-ten date for 28°F is May 24, 13 days before the 32°F one. The freeze-free season lasts 124 days in a typical year, shorter than at 64% of the 110 Colorado stations; it reaches 142 days one year in ten and falls short of 105 one year in ten. On average 202 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 13 days longer, to about June 5, and return around September 16. Severe cold of 16°F or below comes every winter, usually between November 3 and March 29.

July is the warmest month at Rifle 3ENE, CO, averaging 88°F by day and 52°F at night; January is the coldest at 37°F and 10°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 25% of years.

Warmth for growing adds up to 2,130 growing degree days a year (base 50°F), fewer than at 58% of the 110 Colorado stations. 29% of them (615) have built up by the end of June, and July adds the most, 626. Precipitation totals 12.7 inches a year, most in October (1.5") and least in November (0.7"); May to September bring 47% of it.

The nearest other station, Rifle Garfield Co Airport, CO, 10 miles west of New Castle, has a last frost 12 days earlier (May 11), a first frost 9 days later (October 4), a season 19 days longer.

The first measurable snow (0.1 inch or more) in New Castle usually arrives around November 6, and the last of the season around April 15. Those are the middle dates across the winters of 1991–2020 at Rifle 3ENE, CO, 9.4 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 38 days after the last snow.

ZIP 81647 is 9 miles from Rifle 3ENE, CO, which stands at 5,469 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 81650 (Rifle). The 2023 USDA Plant Hardiness Zone Map lists ZIP 81647 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.