Alamo, CA climate
Alamo has mild winters and warm summers, with very little rain. A typical July afternoon reaches 86°, a January night drops to 39°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Alamo feels like
Winter
Spring
Summer
Fall
Alamo weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 56° | 39° | 4.2" | 0 | 11 | 0 | 44° – 55° |
| February | 61° | 42° | 3.8" | 0 | 11 | 0 | 45° – 57° |
| March | 65° | 44° | 3.1" | 0 | 11 | 0 | 48° – 61° |
| April | 69° | 46° | 1.4" | 0 | 7 | 0 | 53° – 61° |
| May | 75° | 50° | 0.6" | 0 | 4 | 0 | 56° – 70° |
| June | 82° | 54° | 0.1" | 0 | 1 | 0 | 63° – 71° |
| July | 86° | 56° | 0.0" | 0 | 0 | 0 | 68° – 75° |
| August | 86° | 57° | 0.0" | 0 | 0 | 0 | 68° – 76° |
| September | 84° | 55° | 0.1" | 0 | 1 | 0 | 65° – 73° |
| October | 76° | 50° | 1.0" | 0 | 3 | 0 | 60° – 71° |
| November | 64° | 44° | 2.0" | 0 | 8 | 0 | 47° – 59° |
| December | 56° | 39° | 4.2" | 0 | 12 | 0 | 44° – 51° |
| Year | 72° | 48° | 20.5" | 0.0" | 68 | 0 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Alamo
Alamo gets 20 inches of rain and melted snow a year. January is the wettest month and July the driest. Rain or snow falls on about 68 days a year.
About 282 frost-free days a year
In half of years the last 32° night comes by March 8 and the first one by December 22. That leaves about 282 frost-free days for gardens, longer than 94% of U.S. towns.
Heating and cooling a home in Alamo
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Alamo, 78% of that work is heating and 22% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Alamo and its neighbors
Alamo borders 4 towns with climate data. January nights across them vary by 3.0°. Walnut Creek has both the coldest January nights (39°) and the hottest July afternoons (87°). Alamo’s January low is 39° and its July high 86°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Alamo compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Alamo averaged 1.6° warmer than the 1900s. The biggest change is in January (+2.2°). The shift is larger than in 78% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Alamo’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. May swings the most: between 1991 and 2020 its average temperature ranged from 56° to 70°. December is the most reliable, staying within 7°.
Common questions about Alamo’s climate
What is the coldest month in Alamo?
December, with a typical high of 56° and a low of 39°.
What is the hottest month in Alamo?
July, with a typical high of 86° and a low of 56°. About 27 days a year reach 90°.
How much snow does Alamo get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in Alamo?
In half of years the first 32° night comes by December 22, and the last spring frost by March 8.
What is the rainiest month in Alamo?
January, with 4.2 inches of rain and melted snow. The year totals 20 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Alamo itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Upper San Leandro Filters, CA (10 mi, snow) and Mt Diablo Junction, CA (5 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.