Photo: Finetooth · CC BY-SA 3.0Precipitation in Grass Valley trails that of 93% of U.S. towns: 15 inches a year
Sunny July days climb to about 85°. By January nights alone, it runs milder than 67% of U.S. towns. Since 1901–2000, the year has warmed by 1.4°, most of all in January. Central heating does most of its work from October to April, in months below 50° on average.
A year in Grass Valley at a glance
Each month’s typical high and low, and what it brings.
What stands out about Grass Valley’s climate
Compared with towns across the U.S., with Grass Valley’s place in Oregon beside it.
What a year in Grass Valley feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 143 frost-free days a year
In half of years the last 32° night comes by May 12 and the first by October 4. Frost and day counts come from NOAA’s station at Moro, OR, 9 miles from the town’s center, 410 ft lower.
The 2023 USDA map puts Grass Valley’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 4°. 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 17 inches of snow a winter
Snow, measured at Moro, OR, falls mostly in January and December. Precipitation (rain plus melted snow) adds up to 15 inches a year; December is the wettest month and July the driest. Rain or snow falls on about 90 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Grass Valley
94% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Moro, OR.
Living with Grass Valley’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
143 frost-free days in zone 7a. The last frost comes by May 12 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 4.
Months with highs of 62–84° and lows of 40° or more: May, June and September.
Parks & trails →Of the yearly building losses FEMA expects in Grass Valley from natural hazards, wildfire is the largest share (58%); heat waves, cold waves, winter storms and ice storms together are 8%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Grass Valley and similar climates
TownRatings has no climate map of the towns around Grass Valley yet.
Climates most like Grass Valley’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 |
|---|---|---|---|---|
| Grass Valley, OR | 27° | 85° | 15" | 17" |
| Indian Hills, NV | 25° | 86° | 14" | 14" |
| Silver City, NM | 26° | 87° | 16" | 13" |
| Hamilton, MT | 20° | 86° | 13" | 17" |
| Pullman, WA | 27° | 84° | 20" | 33" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Grass Valley averaged 1.4° warmer than the 1900s. The biggest change is in January (+3.9°).
A bigger shift than in 54% 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 Grass Valley compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Grass Valley’s place among Oregon’s.
Grass Valley weather by month
Highs, lows and precipitation from NOAA’s grid at Grass Valley’s center; snow, wet days and snow on the ground from Moro, OR. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 40° | 27° | 1.9" | 5.3" | 11 | 10 | 22° – 39° |
| February | 44° | 28° | 1.4" | 2.5" | 9 | 4 | 26° – 42° |
| March | 51° | 31° | 1.4" | 0.7" | 10 | 1 | 34° – 47° |
| April | 58° | 35° | 1.4" | 0.0" | 9 | 0 | 42° – 53° |
| May | 67° | 42° | 1.4" | 0.0" | 8 | 0 | 49° – 60° |
| June | 74° | 47° | 0.9" | 0.0" | 5 | 0 | 56° – 69° |
| July | 85° | 53° | 0.3" | 0.0" | 2 | 0 | 60° – 73° |
| August | 84° | 54° | 0.3" | 0.0" | 2 | 0 | 64° – 74° |
| September | 76° | 48° | 0.5" | 0.0" | 3 | 0 | 58° – 66° |
| October | 61° | 39° | 1.4" | 0.2" | 8 | 0 | 45° – 55° |
| November | 47° | 31° | 2.0" | 2.2" | 12 | 2 | 33° – 45° |
| December | 39° | 26° | 2.2" | 5.7" | 12 | 7 | 26° – 36° |
| Year | 60° | 38° | 15.0" | 16.6" | 90 | 24 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 22° to 39°. September is the most reliable, staying within 7°.
Where Grass Valley’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 Grass Valley’s center.
- Snow: Moro, OR.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Moro, OR, 9 miles from the town’s center, 410 ft lower; 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 Grass Valley’s climate
What is the weather like in Grass Valley?
A typical July afternoon reaches 85°, a January night drops to 27°, and about 17 inches of snow falls in a normal winter. Milder January nights than 67% of U.S. towns; cooler July afternoons than 54% of U.S. towns.
How cold does it get in Grass Valley in winter?
December nights average 26°. About 126 nights a year reach 32° or below and 1 reach 0° or below. In the coldest December of the last 30 years the month averaged 26°.
How much snow does Grass Valley get?
About 17 inches in a normal winter at Moro, OR, most of it in January and December, with snow on the ground about 24 days a year.
How hot does it get in Grass Valley?
July, with a typical high of 85° and a low of 53°. About 22 days a year reach 90° and 2 reach 100° (Moro, OR).
When is the first and last frost in Grass Valley?
In half of years the last spring frost (32°) comes by May 12 and the first fall frost by October 4, about 143 frost-free days, at Moro, OR.
What growing zone is Grass Valley in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 4°.
What is the best time of year to visit Grass Valley?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Grass Valley getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 54% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Grass Valley.
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.