Santa Rosa, California climate: Normal weather by month, frost dates and records
Santa Rosa's normal year runs from 37°F December nights to 84°F August afternoons, with 33.8 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 14.5°C, December lows of 3°C, August highs of 29°C, 858 mm of precipitation a year.
- NOAA stationSanta Rosa Sonoma County Airport
- Station IDUSW00023213
- Location38.50°N 122.81°W
- Elevation114 ft (35 m)
- Population177,524
On October 23, the normal high in Santa Rosa is 75°F and the normal low 44°F, and the chance of measurable rain or snow is 18%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Santa Rosa.
- Jan 58° 38°
- Feb 62° 39°
- Mar 65° 41°
- Apr 69° 43°
- May 75° 47°
- Jun 82° 50°
- Jul 84° 52°
- Aug 84° 52°
- Sep 83° 50°
- Oct 77° 46°
- Nov 65° 40°
- Dec 58° 37°
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 Santa Rosa each month?
August is the warmest month, with normal highs of 84°F; December the coldest, with normal lows of 37°F. The most precipitation falls in December (6.76 in), the least in July (0.01 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 | 58°F | 38°F | 47.7°F | 6.67 | 12 | <1 | 9 | 9 h 50 min |
| February | 62°F | 39°F | 50.5°F | 6.67 | 11 | <1 | 5 | 10 h 40 min |
| March | 65°F | 41°F | 53.3°F | 4.58 | 11 | <1 | 1 | 11 h 50 min |
| April | 69°F | 43°F | 56.1°F | 2.10 | 8 | 1 | 1 | 13 h 10 min |
| May | 75°F | 47°F | 60.7°F | 1.27 | 4 | 2 | <1 | 14 h 10 min |
| June | 82°F | 50°F | 65.9°F | 0.31 | 2 | 6 | <1 | 14 h 50 min |
| July | 84°F | 52°F | 67.6°F | 0.01 | <1 | 7 | <1 | 14 h 40 min |
| August | 84°F | 52°F | 68.0°F | 0.05 | <1 | 7 | <1 | 13 h 40 min |
| September | 83°F | 50°F | 66.5°F | 0.13 | 2 | 8 | <1 | 12 h 30 min |
| October | 77°F | 46°F | 61.3°F | 1.65 | 4 | 3 | <1 | 11 h 20 min |
| November | 65°F | 40°F | 52.8°F | 3.58 | 9 | <1 | 4 | 10 h 10 min |
| December | 58°F | 37°F | 47.2°F | 6.76 | 13 | <1 | 11 | 9 h 30 min |
| Year (annual) | 72°F | 45°F | 58.1°F | 33.78 | 76 | 34 | 31 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 14°C | 3°C | 8.7°C | 169 mm |
| February | 17°C | 4°C | 10.3°C | 169 mm |
| March | 18°C | 5°C | 11.8°C | 116 mm |
| April | 21°C | 6°C | 13.4°C | 53 mm |
| May | 24°C | 8°C | 15.9°C | 32 mm |
| June | 28°C | 10°C | 18.8°C | 8 mm |
| July | 29°C | 11°C | 19.8°C | 0 mm |
| August | 29°C | 11°C | 20.0°C | 1 mm |
| September | 29°C | 10°C | 19.2°C | 3 mm |
| October | 25°C | 8°C | 16.3°C | 42 mm |
| November | 19°C | 5°C | 11.6°C | 91 mm |
| December | 14°C | 3°C | 8.4°C | 172 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Santa Rosa's own co-op station Santa Rosa station does: 0 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USW00023213; 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 Santa Rosa?
Normal highs sit between 65°F and 85°F in March, April, May, June, July, August, September, October and November. Of those, August has the fewest days with rain (0).
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 USW00023213.
When is the last frost in Santa Rosa?
In Santa Rosa, the last spring frost (32°F) comes after March 2 in half of years and after April 2 in one year in ten; the first autumn frost comes before November 20 in half of years and before November 1 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 21 year in 10 after April 2; 9 in 10 after January 27
- First autumn frost, half of years before
- November 201 year in 10 before November 1; 9 in 10 before December 10
NOAA puts the median frost-free season at 262 days, and the season without a hard freeze (28°F) at 321 days.
A hard freeze (28°F) comes after January 23 in half of springs and before December 5 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Santa Rosa in zones 9a to 9b across its 6 ZIP code areas (9b in 95409, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Santa Rosa's NOAA station is in zone 9a: the coldest night of a typical year reaches 24°F (22 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in California · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00023213; 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 Santa Rosa ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Santa Rosa's 6 ZIP code areas run from zone 9a to 9b: 4 in 9a and 2 in 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 Santa Rosa?
In a normal year in Santa Rosa, 34 days a year reach 90°F (4 of them 100°F or more), 31 nights fall to 32°F or colder and 76 days bring measurable precipitation.
- Days at 90°F or more
- 34a normal year
- Days at 100°F or more
- 4a normal year
- Nights at 32°F or colder
- 31a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 76a normal year
The highest temperature in this station's record (since 1998) is 114°F, on September 6, 2022; the lowest is 19°F, on December 9, 2013.
The wettest calendar year on that record is 2019, with 51.96 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00023213; records: ACIS (NOAA Regional Climate Centers), station USW00023213. Records use complete months only; a month missing more than three days is left out.
How sunny is Santa Rosa?
Over a year 87% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Santa Rosa, 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 Santa Rosa need?
A normal year in Santa Rosa brings 2,904 heating degree days, 46% fewer than the median U.S. place (5,373), and 410 cooling degree days, 55% fewer than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,302 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 536 | 0 |
| February | 405 | 0 |
| March | 365 | 1 |
| April | 271 | 4 |
| May | 156 | 21 |
| June | 45 | 74 |
| July | 16 | 97 |
| August | 12 | 105 |
| September | 37 | 82 |
| October | 141 | 26 |
| November | 368 | 1 |
| December | 552 | 0 |
| Year (annual) | 2,904 | 410 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00023213. 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 Santa Rosa been warmer than normal lately?
2025 averaged 58.7°F, 0.6°F above the 1991-2020 normal of 58.1°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 58.0°F | −0.1°F | 30.00 |
| 2022 | 58.6°F | +0.5°F | 16.63 |
| 2023 | 58.2°F | +0.1°F | 43.70 |
| 2024 | 59.8°F | +1.7°F | 51.08 |
| 2025 | 58.7°F | +0.6°F | 28.79 |
Source: observed years: ACIS, station USW00023213. A year counts only with all twelve months complete.
How does Santa Rosa's climate compare?
Santa Rosa is warmer than 62 of the other 218 places with their own NOAA record in California, and wetter than 173. Across the 7,247 U.S. stations with normals, its annual mean of 58.1°F is warmer than 69%.
In the Köppen classification computed from these normals, Santa Rosa is Csb: temperate, dry-summer, warm 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 Santa Rosa share this climate record?
3 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.
- Windsor, CA25,846 people · 3 mi N
- Larkfield-Wikiup, CA8,861 people · 3 mi E
- Fulton, CA637 people · 2 mi E
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Santa Rosa's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Santa Rosa. This page uses Santa Rosa Sonoma County Airport; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Santa Rosa station USC00047965 | 6 mi SE | 166 ft | 59.0°F | 38°F | 82°F | 31.5 | 0 | February 25 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Santa Rosa's climate
What is the coldest month in Santa Rosa?
December, with a normal high of 58°F and a normal low of 37°F. The warmest is August (84°F by day, 52°F at night).
Does it snow in Santa Rosa?
Rarely. NOAA publishes no 1991-2020 snowfall normal for Santa Rosa's NOAA station; Santa Rosa's own co-op station Santa Rosa station records 0 inches of snow in a normal year.
What is the rainiest month in Santa Rosa?
December, with 6.76 in of precipitation in a normal year; the driest is July with 0.01 in.
What plant hardiness zone is Santa Rosa in?
The USDA's 2023 map puts Santa Rosa in zones 9a to 9b across its 6 ZIP code areas (9b in 95409, the largest). By the same method at Santa Rosa's NOAA station, the coldest night of a typical year reaches 24°F (22 years, 1991-2020): zone 9a.
How late can frost come in Santa Rosa?
In half of years the last 32°F night comes after March 2; in one year in ten it comes after April 2. Waiting until April 2 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Santa Rosa in OctoberThis month day by day, its records and recent years
- California climateThe statewide normals and every place in the state
- Graton, CA6 miles from this station, 57.8°F a year
- Healdsburg, CA9 miles from this station, 60.2°F a year
- Occidental, CA12 miles from this station, 57.6°F a year
- Calistoga, CA13 miles from this station, 60.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made