San Geronimo sits near the bottom of U.S. towns for July heat
January nights here settle around 42°. Winters are mild: January nights here are milder than in 90% of U.S. towns. Decade by decade the climate has edged up, 1.5° above 1901–2000. Radiators earn their keep from December to January, the months that average under 50°.
A year in San Geronimo at a glance
Each month’s typical high and low, and what it brings.
What stands out about San Geronimo’s climate
Compared with towns across the U.S., with San Geronimo’s place in California beside it.
What a year in San Geronimo feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
A freeze most winters
Day counts come from NOAA’s station at Kentfield, CA, 7 miles from the town’s center, 490 ft lower; frost dates and degree days from San Rafael Civic Ctr, CA, 7 miles away.
The 2023 USDA map puts San Geronimo’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 30°. 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 38 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 Geronimo
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 Geronimo’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: April, May, June, July, August, September, October and November. 6.6 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in San Geronimo from natural hazards, river flooding is the largest share (59%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →San Geronimo and similar climates
TownRatings has no climate map of the towns around San Geronimo yet.
Climates most like San Geronimo’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 Geronimo, CA | 42° | 76° | 38" | 0.0" |
| Wollochet, WA | 36° | 77° | 43" | 0.3" |
| Scappoose, OR | 34° | 81° | 41" | 0.8" |
| Makawao, HI | 53° | 75° | 23" | 0.0" |
| Swannanoa, NC | 27° | 83° | 48" | 2.1" |
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 San Geronimo averaged 1.5° warmer than the 1900s. The biggest change is in January (+2.4°).
A bigger shift than in 60% 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 Geronimo compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with San Geronimo’s place among California’s.
San Geronimo weather by month
Highs, lows and precipitation from NOAA’s grid at San Geronimo’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 | 56° | 42° | 7.4" | 0.0" | 14 | 0 | 45° – 55° |
| February | 58° | 42° | 7.2" | 0.0" | 13 | 0 | 45° – 56° |
| March | 61° | 43° | 5.2" | 0.0" | 12 | 0 | 47° – 58° |
| April | 63° | 44° | 2.5" | 0.0" | 9 | 0 | 49° – 57° |
| May | 67° | 47° | 1.2" | 0.0" | 5 | 0 | 53° – 63° |
| June | 73° | 50° | 0.3" | 0.0" | 4 | 0 | 58° – 64° |
| July | 76° | 53° | 0.0" | 0.0" | 2 | 0 | 61° – 69° |
| August | 77° | 54° | 0.1" | 0.0" | 3 | 0 | 63° – 69° |
| September | 77° | 53° | 0.1" | 0.0" | 3 | 0 | 62° – 69° |
| October | 72° | 50° | 1.8" | 0.0" | 6 | 0 | 58° – 67° |
| November | 62° | 45° | 4.0" | 0.0" | 10 | 0 | 48° – 57° |
| December | 56° | 42° | 8.1" | 0.0" | 15 | 0 | 45° – 53° |
| Year | 67° | 47° | 37.7" | 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 58°. June is the most reliable, staying within 6°.
Where San Geronimo’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 Geronimo’s center.
- Snow: Muir Woods, CA.
- Frost dates, heating and cooling: San Rafael Civic Ctr, CA, 7 miles away.
- Freezing nights, 90° and 100° days: Kentfield, CA, 7 miles from the town’s center, 490 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 San Geronimo’s climate
What is the weather like in San Geronimo?
A typical July afternoon reaches 76°, a January night drops to 42°, 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 Geronimo in winter?
January nights average 42°. About 5 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 Geronimo 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 Geronimo?
July, with a typical high of 76° and a low of 53°. About 27 days a year reach 90° and 3 reach 100° (San Rafael Civic Ctr, CA).
When is the first and last frost in San Geronimo?
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 Geronimo in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 30°.
What is the best time of year to visit San Geronimo?
By one simple rule (highs of 62–84° and lows of 40° or more), 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 Geronimo getting warmer?
Yes: 1991–2020 averaged 1.5° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 60% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in San Geronimo.
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.