Costa Mesa Climate by Month
Costa Mesa, California, United States
Mild all year, with little rain, mostly from December to March.
The climate in Costa Mesa is mild all year, with little rain, mostly from December to March. Afternoon highs range from 66°F (19°C) in February to 77°F (25°C) in September, and December nights average 47°F (8°C). It gets only 11 in (278 mm) of rain a year. May to September are almost completely dry.
- Warmest month
- 77°F(25°C)
- Average high, September
- Coldest nights
- 47°F(8°C)
- Average low, December
- Rain per year
- 11 in(278 mm)
- Wettest: February
- Humidity
- 62%
- Sunniest: July
Best and worst months in Costa Mesa
Best for weatherThe most comfortable weather comes in July, August and October, with highs around 76°F (24°C) and almost no rain.
Least pleasantJanuary and February are the least pleasant; February is the coldest, with highs of only 66°F (19°C).
Comfort combines how close the afternoon high is to 75°F (24°C) with how much rain falls and how humid it is. See where the weather is best in July.
Temperature and rain through the year
Highs and lows (°F)
Average highAverage low
Rain (in per month)
Costa Mesa weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 67°F(19°C) | 47°F(9°C) | 2.3 in(58 mm) | 57% | 2.8 |
| FebFebruary | 66°F(19°C) | 49°F(9°C) | 2.7 in(68 mm) | 56% | 3.3 |
| MarMarch | 67°F(19°C) | 50°F(10°C) | 1.7 in(42 mm) | 66% | 4.8 |
| AprApril | 69°F(21°C) | 52°F(11°C) | 0.7 in(17 mm) | 61% | 6.0 |
| MayMay | 70°F(21°C) | 56°F(14°C) | 0.2 in(5 mm) | 66% | 6.2 |
| JunJune | 72°F(22°C) | 60°F(16°C) | 0.1 in(2 mm) | 68% | 6.5 |
| JulJulyBest | 75°F(24°C) | 63°F(17°C) | 0.0 in(1 mm) | 70% | 6.6 |
| AugAugustBest | 77°F(25°C) | 64°F(18°C) | 0.0 in(1 mm) | 67% | 6.4 |
| SepSeptember | 77°F(25°C) | 62°F(17°C) | 0.2 in(4 mm) | 65% | 5.3 |
| OctOctoberBest | 75°F(24°C) | 58°F(14°C) | 0.4 in(10 mm) | 59% | 4.0 |
| NovNovember | 71°F(22°C) | 51°F(11°C) | 0.8 in(21 mm) | 54% | 3.2 |
| DecDecember | 66°F(19°C) | 47°F(8°C) | 1.9 in(49 mm) | 51% | 2.6 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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