Frost Dates for 96052 — Lewiston, California

Half of springs at Trinity Rvr Hatchery, CA see their last 32°F night by April 23; only one in ten is past it by April 3, and one in ten still has one after May 11. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 11 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 93% of the 220 California stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 22 in half of years, as early as October 4 one year in ten, and holds off past November 13 one year in ten. A hard freeze of 28°F follows 15 days later, around November 6; in spring the one-in-ten date for 28°F is April 19, 22 days before the 32°F one. The freeze-free season lasts 178 days in a typical year, shorter than at 87% of the 219 California stations; it reaches 208 days one year in ten and falls short of 153 one year in ten. On average 78 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 May 11, and return around October 4. Nights of 24°F, cold enough to damage hardier plants, come in 94% of winters and 16°F in 16%.

July is the warmest month at Trinity Rvr Hatchery, CA, averaging 96°F by day and 54°F at night; December is the coldest at 48°F and 32°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 26% of years.

Warmth for growing adds up to 3,336 growing degree days a year (base 50°F), fewer than at 76% of the 283 California stations. 32% of them (1,064) have built up by the end of June, and July adds the most, 769. Precipitation totals 32.5 inches a year, most in December (6.5") and least in August (0.1"); May to September bring 10% of it.

The nearest other station, Weaverville, CA, 7 miles west of Lewiston and 197 feet higher, has a last frost 10 days later (May 3), a first frost 11 days earlier (October 11), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Lewiston usually arrives around December 12, and the last of the season around February 5. Those are the middle dates across the winters of 1991–2020 at Trinity Rvr Hatchery, CA, 1.6 miles away: half of years saw snow earlier, half later. Snow fell in 83% of those winters. The last 32°F night of spring typically comes 77 days after the last snow.

ZIP 96052 is 2 miles from Trinity Rvr Hatchery, CA, which stands at 1,861 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 96052 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.