Frost Dates for 94904 — Greenbrae, California

In the 86% of winters that bring a 32°F night, half of springs at Kentfield, CA see their last 32°F night by January 16; only one in ten is past it by December 21, 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 9% and after January 16 43%. The 40 days between the even-odds date and the one-in-ten date is wider than at 85% 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 18 in half of years, as early as November 30 one year in ten, and holds off past January 19 one year in ten. A hard freeze of 28°F is less common: it came in 27% of winters. The freeze-free season lasts 334 days in a typical year, longer than at 85% of the 219 California stations; it reaches 365 days one year in ten and falls short of 292 one year in ten. On average 5 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 48 days longer, to about March 5, and return around November 29. A 24°F night is unusual: 2% of winters had one.

August is the warmest month at Kentfield, CA, averaging 83°F by day and 54°F at night; December is the coldest at 56°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 26% of years.

Warmth for growing adds up to 3,578 growing degree days a year (base 50°F), fewer than at 71% of the 283 California stations. 38% of them (1,346) have built up by the end of June, and August adds the most, 567. Precipitation totals 44.5 inches a year, most in December (9.8") and least in July (0.0"); May to September bring 4% of it.

The nearest other station, San Rafael Civic Ctr, CA, 3 miles north of Greenbrae, has a last frost 5 days earlier (January 11), a first frost 3 days later (December 21), a season 15 days longer.

Measurable snow is rare here: only 0 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Kentfield, CA, 0.5 miles away, so there is no typical first-snow date to plan around.

ZIP 94904 is under a mile from Kentfield, CA, which stands at 145 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 94901 (San Rafael). The 2023 USDA Plant Hardiness Zone Map lists ZIP 94904 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.