Grass Valley, California climate: Normal weather by month, frost dates and records
Grass Valley's normal year runs from 33°F December nights to 88°F July afternoons, with 53.2 inches of precipitation and 9 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 13.4°C, December lows of 0°C, July highs of 31°C, 1,351 mm of precipitation a year.
- NOAA stationGrass Valley #2
- Station IDUSC00043573
- Location39.20°N 121.07°W
- Elevation2,400 ft (732 m)
- Population14,085
On October 22, the normal high in Grass Valley is 70°F and the normal low 43°F, and the chance of measurable rain or snow is 17%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Grass Valley.
- Jan 54° 33°
- Feb 55° 34°
- Mar 58° 37°
- Apr 63° 40°
- May 71° 47°
- Jun 80° 53°
- Jul 88° 58°
- Aug 87° 57°
- Sep 82° 52°
- Oct 72° 44°
- Nov 60° 37°
- Dec 53° 33°
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 Grass Valley each month?
July is the warmest month, with normal highs of 88°F; December the coldest, with normal lows of 33°F. The most precipitation falls in December (10.48 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. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 54°F | 33°F | 43.4°F | 9.30 | 0.7 | 13 | <1 | 16 | 9 h 40 min |
| February | 55°F | 34°F | 44.5°F | 8.98 | 3.0 | 12 | <1 | 11 | 10 h 40 min |
| March | 58°F | 37°F | 47.5°F | 8.16 | 3.0 | 12 | <1 | 7 | 11 h 50 min |
| April | 63°F | 40°F | 51.3°F | 4.43 | 0.5 | 9 | <1 | 3 | 13 h 10 min |
| May | 71°F | 47°F | 58.8°F | 2.48 | 0.0 | 6 | 1 | <1 | 14 h 20 min |
| June | 80°F | 53°F | 66.4°F | 0.74 | 0.0 | 3 | 5 | <1 | 14 h 50 min |
| July | 88°F | 58°F | 73.1°F | 0.00 | 0.0 | <1 | 14 | <1 | 14 h 40 min |
| August | 87°F | 57°F | 72.1°F | 0.11 | 0.0 | 1 | 12 | <1 | 13 h 50 min |
| September | 82°F | 52°F | 67.2°F | 0.44 | 0.0 | 2 | 5 | <1 | 12 h 30 min |
| October | 72°F | 44°F | 58.2°F | 2.56 | 0.0 | 4 | 1 | 1 | 11 h 10 min |
| November | 60°F | 37°F | 48.4°F | 5.52 | 0.2 | 8 | <1 | 7 | 10 h |
| December | 53°F | 33°F | 42.6°F | 10.48 | 1.2 | 12 | <1 | 17 | 9 h 30 min |
| Year (annual) | 69°F | 44°F | 56.1°F | 53.20 | 8.6 | 82 | 36 | 61 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 12°C | 1°C | 6.3°C | 236 mm | 2 cm |
| February | 13°C | 1°C | 6.9°C | 228 mm | 8 cm |
| March | 14°C | 3°C | 8.6°C | 207 mm | 8 cm |
| April | 17°C | 4°C | 10.7°C | 113 mm | 1 cm |
| May | 22°C | 8°C | 14.9°C | 63 mm | 0 cm |
| June | 27°C | 11°C | 19.1°C | 19 mm | 0 cm |
| July | 31°C | 15°C | 22.8°C | 0 mm | 0 cm |
| August | 31°C | 14°C | 22.3°C | 3 mm | 0 cm |
| September | 28°C | 11°C | 19.6°C | 11 mm | 0 cm |
| October | 22°C | 7°C | 14.6°C | 65 mm | 0 cm |
| November | 15°C | 3°C | 9.1°C | 140 mm | 1 cm |
| December | 11°C | 0°C | 5.9°C | 266 mm | 3 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00043573; 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 Grass Valley?
Normal highs sit between 65°F and 85°F in May, June, September and October. Of those, September has the fewest days with rain (2).
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 USC00043573.
When is the last frost in Grass Valley?
In Grass Valley, the last spring frost (32°F) comes after April 10 in half of years and after April 30 in one year in ten; the first autumn frost comes before November 13 in half of years and before October 26 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
- April 101 year in 10 after April 30; 9 in 10 after March 17
- First autumn frost, half of years before
- November 131 year in 10 before October 26; 9 in 10 before December 1
NOAA puts the median frost-free season at 215 days, and the season without a hard freeze (28°F) at 268 days.
A hard freeze (28°F) comes after March 9 in half of springs and before December 1 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Grass Valley in zone 9a in ZIP code 95945, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Grass Valley's NOAA station is in zone 9a: the coldest night of a typical year reaches 22°F (27 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 USC00043573; 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.
How hot and how cold does it get in Grass Valley?
In a normal year in Grass Valley, 36 days a year reach 90°F (1 of them 100°F or more), 61 nights fall to 32°F or colder and 82 days bring measurable precipitation.
- Days at 90°F or more
- 36a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 61a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 82a normal year
- Days with 1 inch of snow or more
- 3a normal year
The highest temperature in this station's record (since 1966) is 108°F, on July 16, 1972; the lowest is 3°F, on December 10, 1972.
The wettest calendar year on that record is 1983, with 94.42 in; the snowiest season is 1971–72, with 27.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00043573; records: ACIS (NOAA Regional Climate Centers), station USC00043573. Records use complete months only; a month missing more than three days is left out.
How sunny is Grass Valley?
Over a year 87% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Grass Valley, 5.1 kWh per square metre a day. July is the sunniest month (98%) and December the cloudiest (69%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 70% | 2.1 |
| February | 74% | 3.1 |
| March | 76% | 4.3 |
| April | 81% | 5.9 |
| May | 88% | 7.3 |
| June | 94% | 8.3 |
| July | 98% | 8.3 |
| August | 97% | 7.4 |
| September | 95% | 5.9 |
| October | 89% | 4.1 |
| November | 78% | 2.6 |
| December | 69% | 1.9 |
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 Grass Valley need?
A normal year in Grass Valley brings 3,963 heating degree days, 26% fewer than the median U.S. place (5,373), and 749 cooling degree days, 17% fewer than the median (908). Six months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,206 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 671 | 0 |
| February | 573 | 0 |
| March | 544 | 0 |
| April | 410 | 1 |
| May | 218 | 26 |
| June | 66 | 108 |
| July | 5 | 256 |
| August | 5 | 225 |
| September | 49 | 115 |
| October | 231 | 19 |
| November | 497 | 0 |
| December | 694 | 0 |
| Year (annual) | 3,963 | 749 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00043573. 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 Grass Valley been warmer than normal lately?
2025 averaged 57.6°F, 1.5°F above the 1991-2020 normal of 56.1°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 58.1°F | +2.0°F | 50.30 | 22.2 |
| 2022 | 57.3°F | +1.2°F | 37.25 | 0.0 |
| 2023 | 55.7°F | −0.4°F | 52.99 | 25.5 |
| 2024 | 58.0°F | +1.9°F | 61.88 | 0.0 |
| 2025 | 57.6°F | +1.5°F | 52.83 | 0.5 |
Over 50 complete years from 1967 to 2025, the station's annual mean temperature rose at a fitted 4.4°F per century (+0.24°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00043573; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Grass Valley's climate compare?
Grass Valley is warmer than 46 of the other 218 places with their own NOAA record in California, and wetter than 204. Across the 7,247 U.S. stations with normals, its annual mean of 56.1°F is warmer than 64%.
In the Köppen classification computed from these normals, Grass Valley 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 Grass Valley share this climate record?
4 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.
- Alta Sierra, CA7,061 people · 5 mi S
- Lake Wildwood, CA4,967 people · 7 mi W
- Penn Valley, CA1,197 people · 7 mi W
- Rough and Ready, CA659 people · 4 mi NW
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 Grass Valley's climate
What is the coldest month in Grass Valley?
December, with a normal high of 53°F and a normal low of 33°F. The warmest is July (88°F by day, 58°F at night).
Does it snow in Grass Valley?
Yes: 9 inches in a normal year, falling on 3 days with 0.1 inch or more, the most in February (3.0 inches).
What is the rainiest month in Grass Valley?
December, with 10.48 in of precipitation in a normal year; the driest is July with 0.00 in.
What plant hardiness zone is Grass Valley in?
The USDA's 2023 map puts Grass Valley in zone 9a in ZIP code 95945, the nearest ZIP area. By the same method at Grass Valley's NOAA station, the coldest night of a typical year reaches 22°F (27 years, 1991-2020): zone 9a.
How late can frost come in Grass Valley?
In half of years the last 32°F night comes after April 10; in one year in ten it comes after April 30. Waiting until April 30 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Grass Valley in OctoberThis month day by day, its records and recent years
- California climateThe statewide normals and every place in the state
- Nevada City, CA4 miles from this station, 56.2°F a year
- Colfax, CA10 miles from this station, 59.3°F a year
- Dobbins, CA13 miles from this station, 58.7°F a year
- Blue Canyon Airport, CA20 miles from this station, 52.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made