Frost Dates for 96020 — Chester, California

Half of springs at Chester, CA see their last 32°F night by May 28; only one in ten is past it by May 7, and one in ten still has one after June 13. Planting tender crops after June 4 leaves a 30% risk of a frost on them, after June 8 20%, and after June 13 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 98% of the 220 California stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 28 in half of years, as early as September 12 one year in ten, and holds off past October 14 one year in ten. A hard freeze of 28°F follows 20 days later, around October 18; in spring the one-in-ten date for 28°F is May 24, 20 days before the 32°F one. The freeze-free season lasts 124 days in a typical year, shorter than at 96% of the 219 California stations; it reaches 149 days one year in ten and falls short of 100 one year in ten. On average 188 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 18 days longer, to about June 15, and return around September 12. Severe cold of 16°F or below comes every winter, usually between December 1 and March 5.

July is the warmest month at Chester, CA, averaging 86°F by day and 48°F at night; December is the coldest at 41°F and 22°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 39% of years.

Warmth for growing adds up to 1,837 growing degree days a year (base 50°F), fewer than at 95% of the 283 California stations. 24% of them (441) have built up by the end of June, and July adds the most, 532. Precipitation totals 34.4 inches a year, most in December (6.5") and least in August (0.2"); May to September bring 10% of it.

The nearest other station, Canyon Dam, CA, 11 miles southeast of Chester, has a last frost 10 days earlier (May 18), a first frost 10 days later (October 8), a season 19 days longer.

The first measurable snow (0.1 inch or more) in Chester usually arrives around November 17, and the last of the season around April 16. Those are the middle dates across the winters of 1991–2020 at Chester, CA, 1.1 miles away: half of years saw snow earlier, half later. Snow fell in 89% of those winters. The last 32°F night of spring typically comes 42 days after the last snow.

ZIP 96020 is 1 mile from Chester, CA, which stands at 4,530 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 96020 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.