Fairfield, California climate: Normal weather by month, frost dates and records
Fairfield's normal year runs from 40°F December nights to 90°F July afternoons, with 24.5 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 16.5°C, December lows of 5°C, July highs of 32°C, 623 mm of precipitation a year.
- NOAA stationFairfield
- Station IDUSC00042934
- Location38.27°N 122.07°W
- Elevation40 ft (12 m)
- Population122,646
On October 22, the normal high in Fairfield is 76°F and the normal low 51°F, and the chance of measurable rain or snow is 11%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Fairfield.
- Jan 57° 40°
- Feb 62° 43°
- Mar 66° 45°
- Apr 71° 48°
- May 78° 52°
- Jun 85° 56°
- Jul 90° 58°
- Aug 89° 58°
- Sep 87° 57°
- Oct 78° 52°
- Nov 66° 45°
- Dec 57° 40°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Fairfield each month?
July is the warmest month, with normal highs of 90°F; December the coldest, with normal lows of 40°F. The most precipitation falls in December (5.40 in), the least in July (0.00 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 57°F | 40°F | 48.5°F | 4.68 | 10 | <1 | 3 | 9 h 50 min |
| February | 62°F | 43°F | 52.2°F | 4.97 | 10 | <1 | 1 | 10 h 50 min |
| March | 66°F | 45°F | 55.9°F | 3.31 | 9 | <1 | <1 | 11 h 50 min |
| April | 71°F | 48°F | 59.6°F | 1.47 | 5 | 1 | <1 | 13 h 10 min |
| May | 78°F | 52°F | 65.0°F | 0.74 | 3 | 4 | <1 | 14 h 10 min |
| June | 85°F | 56°F | 70.8°F | 0.19 | 1 | 10 | <1 | 14 h 50 min |
| July | 90°F | 58°F | 73.8°F | 0.00 | <1 | 15 | <1 | 14 h 40 min |
| August | 89°F | 58°F | 73.6°F | 0.03 | <1 | 15 | <1 | 13 h 40 min |
| September | 87°F | 57°F | 71.7°F | 0.08 | 1 | 12 | <1 | 12 h 30 min |
| October | 78°F | 52°F | 65.2°F | 1.11 | 3 | 3 | <1 | 11 h 20 min |
| November | 66°F | 45°F | 55.4°F | 2.55 | 7 | <1 | <1 | 10 h 10 min |
| December | 57°F | 40°F | 48.4°F | 5.40 | 10 | <1 | 4 | 9 h 30 min |
| Year (annual) | 74°F | 50°F | 61.7°F | 24.53 | 59 | 60 | 8 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 14°C | 5°C | 9.2°C | 119 mm |
| February | 16°C | 6°C | 11.2°C | 126 mm |
| March | 19°C | 7°C | 13.3°C | 84 mm |
| April | 22°C | 9°C | 15.3°C | 37 mm |
| May | 25°C | 11°C | 18.3°C | 19 mm |
| June | 30°C | 13°C | 21.6°C | 5 mm |
| July | 32°C | 14°C | 23.2°C | 0 mm |
| August | 32°C | 14°C | 23.1°C | 1 mm |
| September | 31°C | 14°C | 22.1°C | 2 mm |
| October | 26°C | 11°C | 18.4°C | 28 mm |
| November | 19°C | 7°C | 13.0°C | 65 mm |
| December | 14°C | 5°C | 9.1°C | 137 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00042934; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Fairfield?
Normal highs sit between 65°F and 85°F in March, April, May, October and November. Of those, October has the fewest days with rain (3).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00042934.
When is the last frost in Fairfield?
In Fairfield, the last spring frost (32°F) comes after January 15 in half of years and after February 16 in one year in ten; the first autumn frost comes before December 14 in half of years and before November 29 in one year in ten. A night at 32°F or colder comes at all in 88% of years here (NOAA).
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- January 151 year in 10 after February 16; 9 in 10 after December 22
- First autumn frost, half of years before
- December 141 year in 10 before November 29; 9 in 10 before January 9
NOAA puts the median frost-free season at 336 days, and the season without a hard freeze (28°F) at 365 days.
A hard freeze (28°F) comes after December 31 in half of springs and before December 24 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Fairfield in zone 9b across its 3 ZIP code areas (9b in 94533, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Fairfield's NOAA station is in zone 9b: the coldest night of a typical year reaches 28°F (20 complete years).
Frost dates for every NOAA station in California · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00042934; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
What hardiness zone is each Fairfield ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Fairfield's 3 ZIP code areas are all in zone 9b. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Fairfield?
In a normal year in Fairfield, 60 days a year reach 90°F (11 of them 100°F or more), 8 nights fall to 32°F or colder and 59 days bring measurable precipitation.
- Days at 90°F or more
- 60a normal year
- Days at 100°F or more
- 11a normal year
- Nights at 32°F or colder
- 8a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 59a normal year
The highest temperature in this station's record (since 1950) is 114°F, on July 24, 2006; the lowest is 15°F, on December 25, 2011.
The wettest calendar year on that record is 2005, with 36.31 in; the snowiest season is 1988–89, with 1.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00042934; records: ACIS (NOAA Regional Climate Centers), station USC00042934. Records use complete months only; a month missing more than three days is left out.
How sunny is Fairfield?
Over a year 87% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Fairfield, 5.1 kWh per square metre a day. July is the sunniest month (95%) and December the cloudiest (72%). Among the 459 U.S. places of 50,000 or more, that ranks tied 58th (with 22 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 74% | 2.3 |
| February | 77% | 3.3 |
| March | 78% | 4.6 |
| April | 84% | 6.1 |
| May | 88% | 7.3 |
| June | 93% | 8.1 |
| July | 95% | 8.0 |
| August | 94% | 7.1 |
| September | 93% | 5.8 |
| October | 88% | 4.2 |
| November | 81% | 2.8 |
| December | 72% | 2.0 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Fairfield need?
A normal year in Fairfield brings 2,307 heating degree days, 57% fewer than the median U.S. place (5,373), and 1,113 cooling degree days, 23% more than the median (908). Three months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,507 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 512 | 0 |
| February | 357 | 0 |
| March | 284 | 2 |
| April | 180 | 19 |
| May | 76 | 76 |
| June | 14 | 187 |
| July | 2 | 273 |
| August | 1 | 268 |
| September | 7 | 209 |
| October | 69 | 77 |
| November | 291 | 3 |
| December | 515 | 0 |
| Year (annual) | 2,307 | 1,113 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00042934. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Fairfield been warmer than normal lately?
2024 averaged 63.9°F, 2.2°F above the 1991-2020 normal of 61.7°F. 3 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 62.5°F | +0.8°F | 27.70 |
| 2022 | 62.6°F | +0.9°F | 14.35 |
| 2023 | 61.1°F | −0.6°F | – |
| 2024 | 63.9°F | +2.2°F | 25.89 |
Over 38 complete years from 1951 to 2024, the station's annual mean temperature rose at a fitted 4.1°F per century (+0.23°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00042934; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Fairfield's climate compare?
Fairfield is warmer than 116 of the other 218 places with their own NOAA record in California, and wetter than 155. Across the 7,247 U.S. stations with normals, its annual mean of 61.7°F is warmer than 79%.
In the Köppen classification computed from these normals, Fairfield is Csa: temperate, dry-summer, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Fairfield share this climate record?
2 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Suisun City, CA29,614 people · 4 mi SE
- Green Valley, CA1,443 people · 5 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Fairfield's climate
What is the coldest month in Fairfield?
December, with a normal high of 57°F and a normal low of 40°F. The warmest is July (90°F by day, 58°F at night).
Does it snow in Fairfield?
Rarely: NOAA's normal is no measurable snow a year.
What is the rainiest month in Fairfield?
December, with 5.40 in of precipitation in a normal year; the driest is July with 0.00 in.
What plant hardiness zone is Fairfield in?
The USDA's 2023 map puts Fairfield in zone 9b across its 3 ZIP code areas (9b in 94533, the largest). By the same method at Fairfield's NOAA station, the coldest night of a typical year reaches 28°F (20 years, 1991-2020): zone 9b.
How late can frost come in Fairfield?
In half of years the last 32°F night comes after January 15; in one year in ten it comes after February 16. Waiting until February 16 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Fairfield in OctoberThis month day by day, its records and recent years
- California climateThe statewide normals and every place in the state
- Vacaville, CA9 miles from this station, 62.1°F a year
- Napa State Hospital, CA11 miles from this station, 60.3°F a year
- Napa, CA12 miles from this station, 57.7°F a year
- Vallejo, CA14 miles from this station, 61.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made