Frost Dates for 96137 — Westwood, California

Half of springs at Canyon Dam, CA see their last 32°F night by May 18; only one in ten is past it by April 30, and one in ten still has one after June 9. Planting tender crops after May 29 leaves a 30% risk of a frost on them, after June 3 20%, and after June 9 10%. The 22 days between the even-odds date and the one-in-ten date is narrower than at 81% 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 8 in half of years, as early as September 24 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 18 days later, around October 26; in spring the one-in-ten date for 28°F is May 16, 24 days before the 32°F one. The freeze-free season lasts 143 days in a typical year, shorter than at 93% of the 219 California stations; it reaches 169 days one year in ten and falls short of 115 one year in ten. On average 159 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 20 days longer, to about June 7, and return around September 24. Severe cold of 16°F or below comes in 99% of winters, usually between December 8 and February 15.

July is the warmest month at Canyon Dam, CA, averaging 86°F by day and 50°F at night; December is the coldest at 41°F and 25°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 83% of years and June still brings one in 26% of years.

Warmth for growing adds up to 2,062 growing degree days a year (base 50°F), fewer than at 93% of the 283 California stations. 25% of them (524) have built up by the end of June, and July adds the most, 567. Precipitation totals 37.2 inches a year, most in December (6.8") and least in July (0.1"); May to September bring 9% of it.

The nearest other station, Chester, CA, 10 miles west of Westwood, has a last frost 10 days later (May 28), a first frost 10 days earlier (September 28), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Westwood usually arrives around November 17, and the last of the season around April 14. Those are the middle dates across the winters of 1991–2020 at Canyon Dam, CA, 8.5 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 34 days after the last snow.

ZIP 96137 is 9 miles from Canyon Dam, CA, which stands at 4,560 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 96137 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.