Frost Dates for 96101 — Alturas, California

Half of springs at Alturas Municipal Airport, CA see their last 32°F night by June 3; only one in ten is past it by May 14, and one in ten still has one after June 24. Planting tender crops after June 12 leaves a 30% risk of a frost on them, after June 17 20%, and after June 24 10%. The 21 days between the even-odds date and the one-in-ten date is narrower than at 84% 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 September 12 in half of years, as early as August 27 one year in ten, and holds off past September 27 one year in ten. A hard freeze of 28°F follows 13 days later, around September 25; in spring the one-in-ten date for 28°F is June 3, 21 days before the 32°F one. The freeze-free season lasts 97 days in a typical year, shorter than at 99% of the 219 California stations; it reaches 124 days one year in ten and falls short of 73 one year in ten. On average 196 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 5 and March 16.

July is the warmest month at Alturas Municipal Airport, CA, averaging 89°F by day and 47°F at night; December is the coldest at 41°F and 20°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 56% of years.

Warmth for growing adds up to 1,839 growing degree days a year (base 50°F), fewer than at 95% of the 283 California stations. 25% of them (468) have built up by the end of June, and July adds the most, 562. Precipitation totals 11.9 inches a year, most in April (1.5") and least in July (0.3"); May to September bring 25% of it.

The first measurable snow (0.1 inch or more) in Alturas usually arrives around November 2, and the last of the season around May 20. Those are the middle dates across the winters of 1991–2020 at Jess Valley, CA, 19.3 miles away: half of years saw snow earlier, half later. Snow fell in 95% of those winters. The last 32°F night of spring typically comes 14 days after the last snow.

ZIP 96101 is 4 miles from Alturas Municipal Airport, CA, which stands at 4,375 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 96101 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.