Sacramento Northern Railway Historic District · Photo: LPS.1 · CC BY-SA 3.0Suisun City reaches 100° on about 11 days a year, more than 92% of U.S. towns
January nights here settle around 40°. Its yearly precipitation falls short of 89% of U.S. towns. Warming shows here too: 1.7° more than in 1901–2000, led by January. Keep the boiler serviced for the months from December to January, which average under 50°.
A year in Suisun City at a glance
Each month’s typical high and low, and what it brings.
What stands out about Suisun City’s climate
Compared with towns across the U.S., with Suisun City’s place in California beside it.
What a year in Suisun City feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 11 days a year reach 100°
And 60 days reach 90°. Frost and day counts come from NOAA’s station at Fairfield, CA, 4 miles from the town’s center, at about the same height.
The 2023 USDA map puts Suisun City’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 27°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 21 inches of rain a year
December is the wettest month and July the driest. Rain falls on about 59 days a year. Snow is rare: about 0.0" in a normal year at Fairfield, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Suisun City
67% of the work is heating. Months averaging under 55° run from November through February.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Fairfield, CA.
Living with Suisun City’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 9b. Frost comes about 9 winters in 10, so the growing year is set by heat, not cold: 11 days at 100° make midsummer the hard season for gardens.
Months with highs of 62–84° and lows of 40° or more: February, March, April, May, October and November. 2.7 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Suisun City from natural hazards, river flooding is the largest share (69%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Suisun City and its neighbors
Every town next door is within a degree of Suisun City in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Suisun City’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Suisun City, CA | 40° | 89° | 21" | 0.0" |
| Sierra Vista Southeast, AZ | 32° | 91° | 15" | 0.7" |
| Ashland, OR | 31° | 91° | 19" | 0.5" |
| Alpine, TX | 30° | 90° | 15" | 2.2" |
| College Place, WA | 30° | 91° | 15" | 7.2" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Suisun City averaged 1.7° warmer than the 1900s. The biggest change is in January (+2.3°).
A bigger shift than in 69% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Suisun City compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Suisun City’s place among California’s.
Suisun City weather by month
Highs, lows and precipitation from NOAA’s grid at Suisun City’s center; snow, wet days and snow on the ground from Fairfield, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 57° | 40° | 4.3" | 0.0" | 10 | 0 | 44° – 53° |
| February | 62° | 42° | 4.1" | 0.0" | 10 | 0 | 48° – 57° |
| March | 67° | 45° | 2.9" | 0.0" | 9 | 0 | 50° – 62° |
| April | 72° | 47° | 1.3" | 0.0" | 5 | 0 | 55° – 64° |
| May | 78° | 52° | 0.7" | 0.0" | 3 | 0 | 58° – 71° |
| June | 86° | 56° | 0.2" | 0.0" | 1 | 0 | 67° – 74° |
| July | 89° | 58° | 0.0" | 0.0" | 0 | 0 | 70° – 77° |
| August | 89° | 57° | 0.0" | 0.0" | 0 | 0 | 70° – 77° |
| September | 86° | 56° | 0.1" | 0.0" | 1 | 0 | 67° – 75° |
| October | 78° | 51° | 1.0" | 0.0" | 3 | 0 | 61° – 70° |
| November | 66° | 44° | 2.2" | 0.0" | 7 | 0 | 48° – 60° |
| December | 57° | 39° | 4.4" | 0.0" | 10 | 0 | 44° – 53° |
| Year | 74° | 49° | 21.1" | 0.0" | 59 | 0 |
How much a month can swing
A normal is an average. May swings the most: from 1991 to 2020 its average ranged from 58° to 71°. June is the most reliable, staying within 7°.
Where Suisun City’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Suisun City’s center.
- Snow: Fairfield, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Fairfield, CA, 4 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Suisun City’s climate
What is the weather like in Suisun City?
A typical July afternoon reaches 89°, a January night drops to 40°, and snow is almost unheard of. Milder January nights than 88% of U.S. towns; hotter July afternoons than 73% of U.S. towns.
How cold does it get in Suisun City in winter?
December nights average 39°. About 8 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 44°.
How much snow does Suisun City get?
About 0.0 inches in a normal winter at Fairfield, CA, so most winters see none.
How hot does it get in Suisun City?
July, with a typical high of 89° and a low of 58°. About 60 days a year reach 90° and 11 reach 100° (Fairfield, CA).
When is the first and last frost in Suisun City?
There is no reliable frost date: a 32° night comes in about 88% of winters at Fairfield, CA, so most years bring a freeze but some pass without one.
What growing zone is Suisun City in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 27°.
What is the best time of year to visit Suisun City?
By one simple rule (highs of 62–84° and lows of 40° or more), February, March, April, May, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Suisun City getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 69% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Suisun City.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.