San Diego, CA Climate & Monthly Averages
San Diego has a semi-arid climate. August is the hottest month, averaging 78° by day; January is the coldest at 64°.
San Diego's climate runs on sunshine and sparse rain
San Diego runs on a dry-summer rhythm: the warmest months are also the driest. June averages 2 mm (0.1 in) while the wet season peaks in January at 2.9 inches (73 mm). Highs range from 64°F (18°C) to 78°F (26°C).
What the dry climate changes
At its warmest, in August, San Diego runs to 78°F (26°C) in the afternoon and back to 66°F (19°C) by dawn. January bottoms out at 64°F (18°C) in daylight, 48°F (9°C) after dark. January is the wettest month at 2.9 inches (73 mm) over 6 days; June is the driest.
Sunshine averages 10.4 hours a day over the year - sunnier than roughly 78% of the cities we track, peaking in July at 12.4 hours. Between the average August and the average January lie 9°C, a narrower spread than about 78% of the cities we track. Across the gridded 2015-2024 daily record, the highest daily maximum for this location was 98°F (37°C) and the lowest daily minimum 35°F (2°C).
More climate facts for San Diego
- Hottest month: August - highs near 78°F (26°C)
- Coldest month: January - highs near 64°F (18°C)
- Decade extremes (2015-2024): 98°F (37°C) high · 35°F (2°C) low
- Wettest month: January (6 rainy days) · Sunniest: July (12.4 h sun/day)
- Climate type: semi-arid
- Annual swing: 9°C between the average warmest and coolest month · day to night: 8°C
- Average humidity: 74%
Heat, cold and scarce precipitation in the dataset
Derived from ERA5 reanalysis data, 2015–2024. Official station records may differ. Need another precipitation unit? Use the rainfall converter.
When the dry weather is easiest to use
Avoiding the hardest heat or cold
The best time to visit San Diego is generally January to June, when temperatures sit either side of the peak heat rather than in it. Daytime temperatures in that window sit near 67°F (19°C), with rain on about 4 days a month. For the same question asked the other way round, see where else is warm in January.
Prepare for sun and cooler nights
Pack for San Diego with light layers that can absorb a mild swing through the day. August nights average 66°F (19°C), so evenings rarely match the afternoons.
Monthly heat and rainfall table
| Month | High | Low | Rain days | Precipitation | Sunshine | Daylight | Wet-day chance | Humidity |
|---|---|---|---|---|---|---|---|---|
| January | 64° | 48° | 6 | 2.9 in | 8.6 h/day | 10.2 h | 20% | 73% |
| February | 65° | 48° | 5 | 2.1 in | 9.3 h/day | 11.0 h | 18% | 70% |
| March | 65° | 51° | 8 | 2.2 in | 10.2 h/day | 11.9 h | 25% | 75% |
| April | 68° | 54° | 3 | 0.8 in | 10.9 h/day | 12.9 h | 11% | 73% |
| May | 68° | 57° | 3 | 0.6 in | 11.0 h/day | 13.8 h | 10% | 75% |
| June | 72° | 61° | 0 | 0.1 in | 11.9 h/day | 14.3 h | 2% | 76% |
| July | 76° | 65° | 0 | 0.2 in | 12.4 h/day | 14.1 h | 1% | 78% |
| August | 78° | 66° | 0 | 0.3 in | 11.7 h/day | 13.3 h | 2% | 78% |
| September | 78° | 65° | 1 | 0.4 in | 10.7 h/day | 12.3 h | 4% | 77% |
| October | 76° | 60° | 2 | 0.4 in | 9.9 h/day | 11.3 h | 7% | 72% |
| November | 70° | 53° | 4 | 1.1 in | 9.4 h/day | 10.4 h | 12% | 65% |
| December | 64° | 48° | 5 | 2.2 in | 8.3 h/day | 10.0 h | 17% | 70% |
How daytime heat and cool nights change by month
Each card shows the average high and low. The bar places that month between San Diego's coldest night and warmest afternoon.
January
- Rain
- 6 days
- Sunshine
- 8.6 h
- Daylight
- 10.2 h
February
- Rain
- 5 days
- Sunshine
- 9.3 h
- Daylight
- 11.0 h
March
- Rain
- 8 days
- Sunshine
- 10.2 h
- Daylight
- 11.9 h
April
- Rain
- 3 days
- Sunshine
- 10.9 h
- Daylight
- 12.9 h
May
- Rain
- 3 days
- Sunshine
- 11.0 h
- Daylight
- 13.8 h
June
- Rain
- 0 days
- Sunshine
- 11.9 h
- Daylight
- 14.3 h
July
- Rain
- 0 days
- Sunshine
- 12.4 h
- Daylight
- 14.1 h
August
- Rain
- 0 days
- Sunshine
- 11.7 h
- Daylight
- 13.3 h
September
- Rain
- 1 day
- Sunshine
- 10.7 h
- Daylight
- 12.3 h
October
- Rain
- 2 days
- Sunshine
- 9.9 h
- Daylight
- 11.3 h
November
- Rain
- 4 days
- Sunshine
- 9.4 h
- Daylight
- 10.4 h
December
- Rain
- 5 days
- Sunshine
- 8.3 h
- Daylight
- 10.0 h
Looking for warmer alternatives? Browse warm places by month, or compare San Diego's coolest part of the year: January, December, February.
Heat and cold across the San Diego year
Spring (March through May)
Spring in San Diego stays on the cool side of mild, with daytime highs averaging 67°F (19°C) and nights around 54°F (12°C); rain comes on about 14 days over the three months. Daylight is generous - around 10.7 hours of sun a day.
Summer (June through August)
Summer is mild and warm here - highs near 75°F (24°C), nights near 64°F (18°C), and precipitation is sparse, near 13 mm (0.5 in) for the season. Daylight is generous - around 12.0 hours of sun a day.
Fall (September through November)
Fall in San Diego is mild and warm, with daytime highs averaging 75°F (24°C) and nights around 59°F (15°C); precipitation is sparse, near 1.9 inches (49 mm) for the season. Daylight is generous - around 10.0 hours of sun a day.
Winter (December through February)
Winter in San Diego is crisp but comfortable, with daytime highs averaging 64°F (18°C) and nights around 48°F (9°C); rain comes on about 16 days over the three months.
How unusual is San Diego?
- Rain or snow reaches the ground on 39 days a year - fewer wet days than all but 6% of the 3496 cities we track.
- Annual precipitation is 13.3 inches (337 mm) - drier than all but 9% of the 3496 cities we track.
These comparisons use the same ten-year window for every city in the dataset.