Photo: Pi.1415926535 · CC BY-SA 4.0Hardly any U.S. towns see fresher July days than San Anselmo
Midwinter brings lows of about 41°. The wettest month is December; the driest is July. Its January nights stay gentler than in 90% of U.S. towns. Comfortable outdoor weather lasts from March to November, with highs of 62–77°.
A year in San Anselmo at a glance
Each month’s typical high and low, and what it brings.
What stands out about San Anselmo’s climate
Compared with towns across the U.S., with San Anselmo’s place in California beside it.
What a year in San Anselmo feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Frost and day counts come from NOAA’s station at San Rafael Civic Ctr, CA, 2.1 miles from the town’s center, at about the same height.
The 2023 USDA map puts San Anselmo’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 29°. 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 34 inches of rain a year
December is the wettest month and July the driest. Rain falls on about 96 days a year. Snow is rare: about 0.0" in a normal year at Muir Woods, CA, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in San Anselmo
84% of the work is heating. Months averaging under 55° run from November through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at San Rafael Civic Ctr, CA.
Living with San Anselmo’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 9b. Frost comes about 7 winters in 10, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: March, April, May, June, July, August, September, October and November. 6.5 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in San Anselmo from natural hazards, river flooding is the largest share (66%). Normals are averages; the hazards page covers the extremes.
Natural hazards →San Anselmo and its neighbors
Sleepy Hollow the hottest July afternoons (76°, 1° warmer). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like San Anselmo’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 |
|---|---|---|---|---|
| San Anselmo, CA | 41° | 75° | 34" | 0.0" |
| Poulsbo, WA | 35° | 75° | 33" | 3.0" |
| Scappoose, OR | 34° | 81° | 41" | 0.8" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Swannanoa, NC | 27° | 83° | 48" | 2.1" |
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 San Anselmo averaged 1.4° warmer than the 1900s. The biggest change is in January (+2.3°).
A bigger shift than in 56% 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 San Anselmo compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with San Anselmo’s place among California’s.
San Anselmo weather by month
Highs, lows and precipitation from NOAA’s grid at San Anselmo’s center; snow, wet days and snow on the ground from Muir Woods, CA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 57° | 41° | 6.8" | 0.0" | 14 | 0 | 45° – 54° |
| February | 60° | 43° | 6.8" | 0.0" | 13 | 0 | 47° – 57° |
| March | 62° | 44° | 4.7" | 0.0" | 12 | 0 | 47° – 59° |
| April | 65° | 45° | 2.1" | 0.0" | 9 | 0 | 51° – 58° |
| May | 68° | 48° | 1.0" | 0.0" | 5 | 0 | 54° – 64° |
| June | 73° | 51° | 0.2" | 0.0" | 4 | 0 | 59° – 64° |
| July | 75° | 52° | 0.0" | 0.0" | 2 | 0 | 60° – 68° |
| August | 77° | 53° | 0.1" | 0.0" | 3 | 0 | 62° – 68° |
| September | 77° | 52° | 0.1" | 0.0" | 3 | 0 | 61° – 69° |
| October | 73° | 49° | 1.5" | 0.0" | 6 | 0 | 58° – 66° |
| November | 63° | 45° | 3.6" | 0.0" | 10 | 0 | 48° – 58° |
| December | 57° | 41° | 7.4" | 0.0" | 15 | 0 | 45° – 53° |
| Year | 67° | 47° | 34.3" | 0.0" | 96 | 0 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 47° to 59°. June is the most reliable, staying within 6°.
Where San Anselmo’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 San Anselmo’s center.
- Snow: Muir Woods, CA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: San Rafael Civic Ctr, CA, 2.1 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 San Anselmo’s climate
What is the weather like in San Anselmo?
A typical July afternoon reaches 75°, a January night drops to 41°, and snow is almost unheard of. Milder January nights than 90% of U.S. towns; cooler July afternoons than 98% of U.S. towns.
How cold does it get in San Anselmo in winter?
January nights average 41°. About 3 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 45°.
How much snow does San Anselmo get?
About 0.0 inches in a normal winter at Muir Woods, CA, so most winters see none.
How hot does it get in San Anselmo?
July, with a typical high of 75° and a low of 52°. About 20 days a year reach 90° and 1 reach 100° (San Rafael Civic Ctr, CA).
When is the first and last frost in San Anselmo?
There is no reliable frost date: a 32° night comes in about 70% of winters at San Rafael Civic Ctr, CA, so most years bring a freeze but some pass without one.
What growing zone is San Anselmo in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 29°.
What is the best time of year to visit San Anselmo?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, June, July, August, September, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is San Anselmo getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 56% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in San Anselmo.
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.