Frost Dates for 94520 — Concord, California

In the 79% of winters that bring a 32°F night, half of springs at Concord Buchanan Field, CA see their last 32°F night by January 9; only one in ten is past it by December 16, and one in ten still has one after February 12. Counting the winters with no freeze at all, the risk of a 32°F night after February 12 is under 8% and after January 9 40%. The 34 days between the even-odds date and the one-in-ten date is wider than at 65% 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 14 in half of years, as early as November 28 one year in ten, and holds off past January 16 one year in ten. A hard freeze of 28°F is less common: it came in 27% of winters. The freeze-free season lasts 343 days in a typical year, longer than at 90% of the 219 California stations; it reaches 365 days one year in ten and falls short of 313 one year in ten. On average 9 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 36 days longer, to about February 14, and return around December 1. A 24°F night is unusual: 2% of winters had one.

August is the warmest month at Concord Buchanan Field, CA, averaging 88°F by day and 59°F at night; January is the coldest at 58°F and 41°F. From March to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 15% of years.

Warmth for growing adds up to 4,568 growing degree days a year (base 50°F), fewer than at 51% of the 283 California stations. 38% of them (1,758) have built up by the end of June, and August adds the most, 733. Precipitation totals 16.1 inches a year, most in January (3.2") and least in July (0.0"); May to September bring 5% of it.

The nearest other station, Concord Wwtp, CA, 2 miles west of Concord, has a last frost 2 days earlier (January 7), a first frost 5 days later (December 19), a season 3 days longer.

Measurable snow is rare here: only 0 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Concord Wwtp, CA, 1.6 miles away, so there is no typical first-snow date to plan around.

ZIP 94520 is under a mile from Concord Buchanan Field, CA, which stands at 18 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 94565 (Pittsburg). The 2023 USDA Plant Hardiness Zone Map lists ZIP 94520 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.