Frost Dates for 95223 — Arnold, California

Half of springs at Calaveras Big Trees, CA see their last 32°F night by May 7; only one in ten is past it by April 18, and one in ten still has one after May 31. Planting tender crops after May 18 leaves a 30% risk of a frost on them, after May 25 20%, and after May 31 10%. The 24 days between the even-odds date and the one-in-ten date is narrower than at 74% of the 220 California stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by October 28 in half of years, as early as October 5 one year in ten, and holds off past November 16 one year in ten. A hard freeze of 28°F follows 17 days later, around November 14; in spring the one-in-ten date for 28°F is May 12, 19 days before the 32°F one. The freeze-free season lasts 169 days in a typical year, shorter than at 88% of the 219 California stations; it reaches 199 days one year in ten and falls short of 139 one year in ten. On average 115 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 23 days longer, to about May 30, and return around October 11. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 58%.

July is the warmest month at Calaveras Big Trees, CA, averaging 81°F by day and 56°F at night; December is the coldest at 44°F and 30°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 60% of years.

Warmth for growing adds up to 2,183 growing degree days a year (base 50°F), fewer than at 91% of the 283 California stations. 24% of them (531) have built up by the end of June, and July adds the most, 561. Precipitation totals 55.7 inches a year, most in January (10.6") and least in July (0.1"); May to September bring 8% of it.

The nearest other station, New Melones Dam Hq, CA, 22 miles southwest of Arnold and 3,735 feet lower, has a last frost 76 days earlier (February 20), a first frost 44 days later (December 11), a season 121 days longer.

The first measurable snow (0.1 inch or more) in Arnold usually arrives around November 27, and the last of the season around April 21. Those are the middle dates across the winters of 1991–2020 at Calaveras Big Trees, CA, 1.3 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 16 days after the last snow.

ZIP 95223 is 1 mile from Calaveras Big Trees, CA, which stands at 4,695 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 95223 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.