Costa Mesa climate — normals and trends
Costa Mesa (United States) has a cold semi-arid climate (BSk) under the Köppen-Geiger classification. Its mean annual temperature is 17.1 °C and it receives 322 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is August (21.8 °C on average) and the coldest is January (12.7 °C). Rainfall peaks in February.
Costa Mesa averages 0 frost days, 16 hot days (≥ 30 °C) and 33 rainy days per year.
Costa Mesa has warmed by +1.4 °C between 1940 and 2025, or +0.17 °C per decade. This trend is statistically significant.
The hottest day of the period reached 40.3 °C (on 4 September 1988) and the coldest -0.4 °C (on 4 January 1949).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
Costa MesaCalifornia
- coords
- 33.64°, -117.92°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
17.1°C
Average daily high
21.8°C
Average daily low
13.4°C
Annual rainfall
322mm
Sunshine / day
11.2h
Mean relative humidity
72%
Average peak wind
15.4km/h
Seasonal range
9.1°C
Frost days (< 0 °C)
0 d/yr
Hot days (≥ 30 °C)
16 d/yr
Rainy days (≥ 1 mm)
33 d/yr
Annual snowfall
0.0 cm
Average feels-like high
21.7 °C
Average feels-like low
12.9 °C
Average peak gust
29.3 km/h
Tropical nights (≥ 20 °C)
11 d/yr
Solar radiation
20.1 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.4 °C
since 1940
+0.2 °C per decade · r² = 0.36 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
40.3 °C
4 September 1988
Coldest day
-0.4 °C
4 January 1949
Wettest day
92 mm
1 March 1983
Windiest day
48.4 km/h
25 February 2023
Strongest gust
83.9 km/h
1 March 1983
Hottest feels-like
41.6 °C
5 September 1984
Coldest feels-like
-5.4 °C
4 January 1949
Snowiest day
0.1 cm
11 January 1949
Sunniest day
14.0 h
9 June 1940
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 18.8 °C | +1.2 °C | 18 mm | -49 mm |
| Feb | 18.9 °C | +0.9 °C | 52 mm | -19 mm |
| Mar | 17.8 °C | -0.8 °C | 49 mm | -4 mm |
| Apr | 19.3 °C | -0.8 °C | 8 mm | -15 mm |
| May | 21.8 °C | +0.5 °C | 5 mm | -2 mm |
| Jun | 23.2 °C | -0.2 °C | 3 mm | +2 mm |
| Jul | 24.1 °C | -2.1 °C | 1 mm | +1 mm |
| Aug | 27.1 °C | +0.2 °C | 0 mm | -2 mm |
| Sep | 26.5 °C | +0.1 °C | 6 mm | +1 mm |
| Oct | 23.6 °C | -0.5 °C | 28 mm | +16 mm |
| Nov | 20.7 °C | -0.3 °C | 116 mm | +85 mm |
| Dec | 19.8 °C | +1.8 °C | 77 mm | +28 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of Costa Mesa?
Costa Mesa has a cold semi-arid climate (Köppen BSk). Over 1940-2025, the average annual temperature is 17.1 °C and it receives 322 mm of precipitation per year.
What is the hottest day ever recorded in Costa Mesa?
The hottest day measured in Costa Mesa between 1940 and 2025 was 4 September 1988, reaching 40.3 °C.
What is the coldest day in Costa Mesa?
The coldest day measured in Costa Mesa between 1940 and 2025 was 4 January 1949, at -0.4 °C.
Does it snow in Costa Mesa?
Almost never: Costa Mesa sees virtually no snow, with about 0 frost days per year.
Has the climate of Costa Mesa warmed?
Yes: Costa Mesa warmed by +1.4 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in Costa Mesa?
The wettest day measured in Costa Mesa between 1940 and 2025 was 1 March 1983, with 92 mm of rain in 24 hours.
What was the windiest day in Costa Mesa?
The windiest day measured in Costa Mesa between 1940 and 2025 was 25 February 2023, with winds reaching 48.4 km/h.
What is the warmest month in Costa Mesa?
The warmest month in Costa Mesa is August (21.8 °C on average); the coldest is January (12.7 °C).
How much does it rain in Costa Mesa?
Costa Mesa receives on average 322 mm of precipitation per year, spread over about 33 rainy days.
Is it sunny in Costa Mesa?
Costa Mesa gets on average 11.2 hours of sunshine per day, roughly 4,088 hours per year over 1940-2025.
What is the biggest single-day snowfall in Costa Mesa?
The heaviest 24-hour snowfall measured in Costa Mesa between 1940 and 2025 was 11 January 1949, with 0.1 cm.
Are there tropical nights in Costa Mesa?
Yes: Costa Mesa has on average 11 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in Costa Mesa?
In Costa Mesa, between 1940 and 2025, the highest apparent temperature reached 41.6 °C on 5 September 1984, and the lowest was -5.4 °C on 4 January 1949.
Compare Costa Mesa with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around Costa Mesa