San Marcos, CA climate
San Marcos has warm winters and pleasant summers, with very little rain. A typical July afternoon reaches 82°, a January night drops to 45°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in San Marcos feels like
Winter
Spring
Summer
Fall
San Marcos 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 | 67° | 45° | 2.5" | 0 | 7 | 0 | 53° – 61° |
| February | 67° | 46° | 2.8" | 0 | 7 | 0 | 53° – 63° |
| March | 68° | 48° | 2.1" | 0 | 6 | 0 | 53° – 64° |
| April | 71° | 50° | 0.8" | 0 | 4 | 0 | 56° – 65° |
| May | 73° | 55° | 0.3" | 0 | 3 | 0 | 60° – 69° |
| June | 77° | 58° | 0.1" | 0 | 1 | 0 | 64° – 71° |
| July | 82° | 62° | 0.1" | 0 | 1 | 0 | 69° – 77° |
| August | 85° | 63° | 0.0" | 0 | 0 | 0 | 71° – 77° |
| September | 83° | 61° | 0.1" | 0 | 1 | 0 | 69° – 77° |
| October | 78° | 56° | 0.6" | 0 | 2 | 0 | 63° – 72° |
| November | 73° | 49° | 1.0" | 0 | 4 | 0 | 54° – 65° |
| December | 67° | 44° | 1.9" | 0 | 6 | 0 | 53° – 59° |
| Year | 74° | 53° | 12.4" | 0.0" | 41 | 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 San Marcos
San Marcos gets 12 inches of rain and melted snow a year. February is the wettest month and August the driest. Rain or snow falls on about 41 days a year.
A year-round growing season
Heating and cooling a home in San Marcos
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In San Marcos, 61% of that work is heating and 39% 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.
San Marcos and its neighbors
San Marcos borders 7 towns with climate data. January nights across them vary by 5.6°. Escondido has both the coldest January nights (42°) and the hottest July afternoons (87°). San Marcos’s January low is 45° and its July high 82°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How San Marcos 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 San Marcos averaged 2.0° warmer than the 1900s. The biggest change is in January (+3.1°). The shift is larger than in 93% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at San Marcos’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. March swings the most: between 1991 and 2020 its average temperature ranged from 53° to 64°. August is the most reliable, staying within 6°.
Common questions about San Marcos’s climate
What is the coldest month in San Marcos?
December, with a typical high of 67° and a low of 44°.
What is the hottest month in San Marcos?
August, with a typical high of 85° and a low of 63°. About 21 days a year reach 90°.
How much snow does San Marcos get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in San Marcos?
Frost is uncommon. Only 21% of years see a night at 32° or below.
What is the rainiest month in San Marcos?
February, with 2.8 inches of rain and melted snow. The year totals 12 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for San Marcos itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Poway Valley, CA (11 mi, snow) and Rancho Bernardo, CA (9 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.