Frost Dates for 94957 — Ross, California

In the 70% of winters that bring a 32°F night, half of springs at San Rafael Civic Ctr, CA see their last 32°F night by January 11; only one in ten is past it by December 14, and one in ten still has one after February 25. Counting the winters with no freeze at all, the risk of a 32°F night after February 25 is under 7% and after January 11 35%. The 45 days between the even-odds date and the one-in-ten date is wider than at 93% 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 December 21 in half of years, as early as December 2 one year in ten, and holds off past February 9 one year in ten. A hard freeze of 28°F is less common: it came in 21% of winters. The freeze-free season lasts 349 days in a typical year, longer than at 93% of the 219 California stations; it reaches 365 days one year in ten and falls short of 304 one year in ten. On average 3 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 42 days longer, to about February 22, and return around December 5. A 24°F night is unusual: 3% of winters had one.

August is the warmest month at San Rafael Civic Ctr, CA, averaging 81°F by day and 56°F at night; December is the coldest at 57°F and 42°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 18% of years.

Warmth for growing adds up to 3,652 growing degree days a year (base 50°F), fewer than at 68% of the 283 California stations. 38% of them (1,371) have built up by the end of June, and August adds the most, 570. Precipitation totals 34.5 inches a year, most in December (7.8") and least in July (0.0"); May to September bring 4% of it.

The nearest other station, Kentfield, CA, 5 miles south of Ross, has a last frost 5 days later (January 16), a first frost 3 days earlier (December 18), a season 15 days shorter.

Measurable snow is rare here: only 0 of 21 winters from 1991 to 2020 recorded 0.1 inch or more at San Rafael Civic Ctr, CA, 2.1 miles away, so there is no typical first-snow date to plan around.

ZIP 94957 is 2 miles from San Rafael Civic Ctr, CA, which stands at 120 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 94903 (San Rafael). The 2023 USDA Plant Hardiness Zone Map lists ZIP 94957 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.