USDA Hardiness Zone 9b
Frost Dates for 94533 — Fairfield, California
NOAA 1991–2020 normals from Fairfield, CA (40 ft), 2 miles west.
Updated
A freeze (32°F) reaches Fairfield in 88% of winters. When it does, the first fall frost comes around December 14 and the last spring frost around January 15; after February 16 the chance of another is under 9%.
- Last spring frost
- January 15
- First fall frost
- December 14
- Winters with a freeze
- 88%
- Hardiness zone
- 9b
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
0 of 24 observed
NOAA normal
Frost risk by date in Fairfield
In the 88% of winters that bring a 32°F night, half of springs at Fairfield, CA see their last 32°F night by January 15; only one in ten is past it by December 22, and one in ten still has one after February 16. Counting the winters with no freeze at all, the risk of a 32°F night after February 16 is under 9% and after January 15 44%. The 32 days between the even-odds date and the one-in-ten date is wider than at 55% 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 29 one year in ten, and holds off past January 9 one year in ten. A hard freeze of 28°F is less common: it came in 44% of winters. The freeze-free season lasts 336 days in a typical year, longer than at 88% of the 219 California stations; it reaches 365 days one year in ten and falls short of 296 one year in ten. On average 8 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 41 days longer, to about February 25, and return around December 1. A 24°F night is unusual: 9% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 23 | Feb 2 | Feb 9 | Feb 17 | Feb 25 | Mar 3 | Mar 11 | Mar 24 | Apr 4 |
| 32°F88% of yrs | Dec 22 | Dec 29 | Jan 3 | Jan 9 | Jan 15 | Jan 21 | Jan 28 | Feb 2 | Feb 16 |
| 28°F44% of yrs | too rare for a date | ||||||||
| 24°F9% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 13 | Nov 19 | Nov 23 | Nov 27 | Dec 1 | Dec 3 | Dec 6 | Dec 12 | Dec 21 |
| 32°F88% of yrs | Nov 29 | Dec 2 | Dec 7 | Dec 11 | Dec 14 | Dec 19 | Dec 25 | Jan 1 | Jan 9 |
| 28°F44% of yrs | too rare for a date | ||||||||
| 24°F9% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| 16°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Fairfield, CA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 94533 →Compare Fairfield with another place →
Weather by month in Fairfield
July is the warmest month at Fairfield, CA, averaging 90°F by day and 58°F at night; December is the coldest at 57°F and 40°F. From March to October 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 4,507 growing degree days a year (base 50°F), fewer than at 53% of the 283 California stations. 38% of them (1,702) have built up by the end of June, and July adds the most, 736. Precipitation totals 24.6 inches a year, most in December (5.4") and least in July (0.0"); May to September bring 4% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 57 | 40 | 4.7 | 58% | 3 | 37 |
| Feb | 62 | 43 | 5.0 | 18% | 1 | 91 |
| Mar | 66 | 45 | 3.3 | 2% | <1 | 195 |
| Apr | 71 | 48 | 1.5 | 1% | <1 | 291 |
| May | 78 | 52 | 0.7 | 0% | 0 | 465 |
| Jun | 85 | 56 | 0.2 | 0% | <1 | 622 |
| Jul | 90 | 58 | 0.0 | 0% | 0 | 736 |
| Aug | 89 | 58 | 0.0 | 0% | 0 | 732 |
| Sep | 87 | 57 | 0.1 | 0% | 0 | 652 |
| Oct | 78 | 52 | 1.1 | 0% | 0 | 473 |
| Nov | 66 | 45 | 2.6 | 11% | <1 | 176 |
| Dec | 57 | 40 | 5.4 | 63% | 4 | 36 |
Monthly normals 1991–2020 at Fairfield, CA (40 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Vacaville Nut Tree Airport, CA, 9 miles northeast of Fairfield, has a last frost 34 days later (February 18), a first frost 16 days earlier (November 28), a season 53 days shorter.
When it snows in Fairfield, California
Measurable snow is rare here: only 0 of 24 winters from 1991 to 2020 recorded 0.1 inch or more at Fairfield, CA, 1.7 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 94533 is 2 miles from Fairfield, CA, which stands at 40 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 94533 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.
Frost dates across California →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.