Frost Dates for 94571 — Rio Vista, California

In the 81% of winters that bring a 32°F night, half of springs at Antioch Pumping Plt #3, CA see their last 32°F night by January 12; only one in ten is past it by December 20, and one in ten still has one after February 1. Counting the winters with no freeze at all, the risk of a 32°F night after February 1 is under 8% and after January 12 41%. The 20 days between the even-odds date and the one-in-ten date is narrower than at 88% of the 220 California stations behind this site's ZIP pages.

In fall the first 32°F night comes by December 19 in half of years, as early as November 29 one year in ten, and holds off past January 12 one year in ten. A hard freeze of 28°F is less common: it came in 35% 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 315 one year in ten. On average 7 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 27 days longer, to about February 8, and return around December 4. A 24°F night is unusual: 5% of winters had one.

July is the warmest month at Antioch Pumping Plt #3, CA, averaging 91°F by day and 61°F at night; January is the coldest at 56°F and 40°F. From February to November the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 4,827 growing degree days a year (base 50°F), more than at 59% of the 283 California stations. 38% of them (1,854) have built up by the end of June, and July adds the most, 806. Precipitation totals 12.7 inches a year, most in January (2.7") and least in July (0.0"); May to September bring 5% of it.

The nearest other station, Vacaville Nut Tree Airport, CA, 20 miles northwest of Rio Vista, has a last frost 37 days later (February 18), a first frost 21 days earlier (November 28), a season 60 days shorter.

Measurable snow is rare here: only 0 of 17 winters from 1991 to 2020 recorded 0.1 inch or more at Antioch Pumping Plt #3, CA, 12.1 miles away, so there is no typical first-snow date to plan around.

ZIP 94571 is 12 miles from Antioch Pumping Plt #3, CA, which stands at 60 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 94509 (Antioch). The 2023 USDA Plant Hardiness Zone Map lists ZIP 94571 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.