Fairfield climate
Fairfield (California, United States) has a warm-summer Mediterranean climate (Köppen Csb). The average temperature over the year is 15 °C60 °F, and about 467 mm18 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Fairfield climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin | Frost days |
|---|---|---|---|---|---|
| Jan | 1457 | 439 | 948 | 863.4 | 4 |
| Feb | 1660 | 541 | 1050 | 813.2 | 1 |
| Mar | 1865 | 643 | 1254 | 702.7 | 0 |
| Apr | 2169 | 745 | 1457 | 381.5 | 0 |
| May | 2476 | 949 | 1762 | 140.5 | 0 |
| Jun | 2984 | 1152 | 2068 | 40.1 | 0 |
| Jul | 3187 | 1254 | 2170 | 00.0 | 0 |
| Aug | 3187 | 1254 | 2170 | 10.0 | 0 |
| Sep | 3086 | 1253 | 2169 | 30.1 | 0 |
| Oct | 2578 | 1050 | 1864 | 220.9 | 0 |
| Nov | 1966 | 744 | 1355 | 481.9 | 1 |
| Dec | 1457 | 439 | 948 | 1014.0 | 4 |
| Year | 3187 | 439 | 1560 | 46718 | 9 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total. Frost days are for the whole grid cell.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 84% | 55% | 2.3 | 9:47 |
| Feb | 81% | 53% | 3.3 | 10:43 |
| Mar | 80% | 52% | 4.6 | 11:51 |
| Apr | 74% | 44% | 6.1 | 13:09 |
| May | 69% | 35% | 7.3 | 14:14 |
| Jun | 62% | 22% | 8.1 | 14:49 |
| Jul | 60% | 19% | 8.0 | 14:34 |
| Aug | 62% | 21% | 7.1 | 13:38 |
| Sep | 59% | 21% | 5.8 | 12:22 |
| Oct | 61% | 31% | 4.2 | 11:07 |
| Nov | 71% | 45% | 2.8 | 10:02 |
| Dec | 80% | 57% | 2.0 | 9:31 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Fairfield is like
The warmest month is July, with an average high of 31 °C87 °F and a low of 12 °C54 °F. The coldest is January, when highs average 14 °C57 °F and lows 4 °C39 °F. There is a clear seasonal cycle, with 12.6 °C22.6 °F between the average temperature of the warmest and the coolest month.
Annual precipitation is moderate at about 467 mm18 in. The wettest three-month stretch is December–February, which brings 57% of the annual total. Months with less than 20 mm0.8 in on average: May–September. The wettest month is December (101 mm4.0 in), the driest is July (0 mm0.0 in).
Relative humidity ranges from 59% in September to 84% in January. The clearest skies (lowest average cloud amount, 19%) are typical of July. Average wind speed near the ground ranges from 6 km/h (4 mph) in January to 14 km/h (9 mph) in July. Daylight lasts from about 9.5 hours in December to 14.8 hours in June.
Best time to visit Fairfield
Based on these averages, the most comfortable months for sightseeing and outdoor activities are April–June and September–November: average highs of 19 °C66 °F to 30 °C86 °F with 3 mm0.1 in to 48 mm1.9 in of precipitation per month.
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Fairfield
- Winter (December–February) — highs 1457 to 16 °C60 °F, lows 439 to 5 °C41 °F, about 89 mm3.5 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket and an extra layer for the cooler mornings and evenings.
- Spring (March–May) — highs 1865 to 24 °C76 °F, lows 643 to 9 °C49 °F, about 40 mm1.6 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
- Summer (June–August) — highs 2984 to 31 °C87 °F, lows 1152 to 12 °C54 °F, about 1 mm0.1 in of precipitation a month. Pack very light, breathable clothing, a sun hat and plenty of water and an extra layer for the cooler mornings and evenings.
- Autumn (September–November) — highs 1966 to 30 °C86 °F, lows 744 to 12 °C53 °F, about 24 mm1.0 in of precipitation a month. Pack light summer clothes such as T-shirts, shorts or light dresses and an extra layer for the cooler mornings and evenings.
How Fairfield compares
Compared with Vallejo, about 25 km to the southwest, Fairfield is on average 1.4 °C2.5 °F warmer and receives 20% less precipitation (467 mm18 in vs 586 mm23 in). The difference is largest in July (4.1 °C7.4 °F warmer).
Of the 222 places in the United States covered by World Climates, Fairfield is the 105th warmest by annual mean temperature and the 171st wettest by annual precipitation. See all of them on the United States climate page.
Places in other countries with the most similar temperature and rainfall pattern: Jerusalem (Israel, Csa), Hebron (Palestine, BSk) and Al Bayda (Libya, BSk).
Nearby places
- Vallejo 25 km · 14 °C57 °F · 586 mm23 in
- Concord 30 km · 15 °C59 °F · 467 mm18 in
- Antioch 34 km · 15 °C60 °F · 467 mm18 in
- Sacramento 60 km · 17 °C63 °F · 567 mm22 in
- San Francisco 62 km · 14 °C57 °F · 586 mm23 in
- Santa Rosa 63 km · 16 °C61 °F · 688 mm27 in
- Hayward 65 km · 15 °C59 °F · 511 mm20 in
- Daly City 71 km · 13 °C55 °F · 516 mm20 in
Frequently asked questions
What is the warmest month in Fairfield?
July is the warmest month in Fairfield, with an average high of 31 °C (87 °F) and an average low of 12 °C (54 °F).
What is the coldest month in Fairfield?
January is the coldest month, with an average high of 14 °C (57 °F) and an average low of 4 °C (39 °F).
When does it rain the most in Fairfield?
December is the wettest month with about 101 mm (4.0 in) of precipitation; July is the driest with about 0 mm (0.0 in).
What is the best time to visit Fairfield?
Judging by long-term averages, the most comfortable months are April–June and September–November.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 105 m, while Fairfield lies at about 4 m. Temperatures on this page were therefore adjusted by +0.7 °C1.2 °F using the standard lapse rate of 6.5 °C per 1,000 m.