Costa Mesa, CA climate
Costa Mesa has warm winters and pleasant summers, with very little rain. A typical July afternoon reaches 78°, a January night drops to 48°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Costa Mesa feels like
Winter
Spring
Summer
Fall
Costa Mesa 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 | 68° | 48° | 2.5" | 0 | 6 | 0 | 55° – 62° |
| February | 67° | 49° | 2.9" | 0 | 7 | 0 | 53° – 64° |
| March | 68° | 51° | 1.6" | 0 | 5 | 0 | 55° – 67° |
| April | 70° | 53° | 0.7" | 0 | 3 | 0 | 58° – 65° |
| May | 71° | 57° | 0.2" | 0 | 2 | 0 | 61° – 69° |
| June | 74° | 60° | 0.1" | 0 | 1 | 0 | 64° – 71° |
| July | 78° | 64° | 0.0" | 0 | 1 | 0 | 67° – 76° |
| August | 80° | 64° | 0.0" | 0 | 0 | 0 | 69° – 75° |
| September | 80° | 63° | 0.1" | 0 | 1 | 0 | 68° – 76° |
| October | 77° | 58° | 0.4" | 0 | 2 | 0 | 64° – 74° |
| November | 73° | 52° | 0.7" | 0 | 3 | 0 | 57° – 65° |
| December | 68° | 47° | 2.0" | 0 | 6 | 0 | 54° – 62° |
| Year | 73° | 55° | 11.2" | 0.0" | 35 | 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 Costa Mesa
Costa Mesa gets 11 inches of rain and melted snow a year. February is the wettest month and August the driest. Rain or snow falls on about 35 days a year.
A year-round growing season
Heating and cooling a home in Costa Mesa
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Costa Mesa, 50% of that work is heating and 50% 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.
Costa Mesa and its neighbors
Costa Mesa borders 4 towns with climate data. January nights across them vary by 2.3°. Irvine has both the coldest January nights (47°) and the hottest July afternoons (83°). Costa Mesa’s January low is 48° and its July high 78°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Costa Mesa 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 Costa Mesa averaged 2.1° warmer than the 1900s. The biggest change is in January (+3.1°). The shift is larger than in 96% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Costa Mesa’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 55° to 67°. August is the most reliable, staying within 6°.
Common questions about Costa Mesa’s climate
What is the coldest month in Costa Mesa?
December, with a typical high of 68° and a low of 47°.
What is the hottest month in Costa Mesa?
September, with a typical high of 80° and a low of 63°. About 13 days a year reach 90°.
How much snow does Costa Mesa get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in Costa Mesa?
Frost is uncommon. Only 0% of years see a night at 32° or below.
What is the rainiest month in Costa Mesa?
February, with 2.9 inches of rain and melted snow. The year totals 11 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Costa Mesa itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Santa Ana Fire Stn, CA (6 mi, snow) and Santa Ana John Wayne Airport, CA (3 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.