Frost Dates for 95436 — Forestville, California

Half of springs at Graton, CA see their last 32°F night by March 20; only one in ten is past it by February 12, and one in ten still has one after April 19. Planting tender crops after April 3 leaves a 30% risk of a frost on them, after April 10 20%, and after April 19 10%. The 30 days between the even-odds date and the one-in-ten date is narrower than at 48% 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 November 13 in half of years, as early as October 26 one year in ten, and holds off past December 6 one year in ten. A hard freeze of 28°F follows 20 days later, around December 3; in spring the one-in-ten date for 28°F is March 7, 43 days before the 32°F one. The freeze-free season lasts 240 days in a typical year, shorter than at 70% of the 219 California stations; it reaches 285 days one year in ten and falls short of 200 one year in ten. On average 43 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 34 days longer, to about April 23, and return around October 24. Nights of 24°F, cold enough to damage hardier plants, come in 55% of winters.

August is the warmest month at Graton, CA, averaging 84°F by day and 50°F at night; December is the coldest at 58°F and 37°F. From May to September the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 77% of years and March still brings one in 66% of years and April still brings one in 33% of years.

Warmth for growing adds up to 3,190 growing degree days a year (base 50°F), fewer than at 80% of the 283 California stations. 37% of them (1,175) have built up by the end of June, and August adds the most, 529. Precipitation totals 40.0 inches a year, most in December (8.3") and least in July (0.0"); May to September bring 5% of it.

The nearest other station, Santa Rosa Sonoma Co Airport, CA, 5 miles east of Forestville, has a last frost 18 days earlier (March 2), a first frost 7 days later (November 20), a season 22 days longer.

Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Graton, CA, 5 miles away, so there is no typical first-snow date to plan around.

ZIP 95436 is 5 miles from Graton, CA, which stands at 200 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 95472 (Sebastopol). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95436 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°C) over 1991–2020; a zone describes winter lows, not frost dates.