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Fullerton Weather by Month
Average temperatures, rainfall and humidity for Fullerton, United States, month by month, built from OpenWeather’s historical records. Use it to see what a typical Fullerton month looks like before you travel — then check the live Fullerton forecast for the days ahead.
Warmest month
August
30°C average high
Coolest month
January
10°C average low
Wettest month
October
93 mm of rain
Driest month
August
2 mm of rain
Average temperature and rainfall in Fullerton by month
Averages of the daily highs and lows recorded in each month, with total rainfall, mean humidity and mean wind speed.
| Month | Avg high | Avg low | Record low / high | Rainfall | Humidity | Wind |
|---|---|---|---|---|---|---|
| January | 20°C | 10°C | 2°C / 32°C | 57 mm | 60% | 8 km/h |
| February | 20°C | 10°C | 2°C / 35°C | 54 mm | 61% | 9 km/h |
| March | 21°C | 11°C | -22°C / 37°C | 40 mm | 65% | 9 km/h |
| April | 23°C | 13°C | 6°C / 37°C | 14 mm | 63% | 9 km/h |
| May | 23°C | 15°C | 8°C / 38°C | 18 mm | 69% | 9 km/h |
| June | 26°C | 17°C | 12°C / 44°C | 3 mm | 71% | 9 km/h |
| July | 30°C | 19°C | 15°C / 44°C | 3 mm | 68% | 9 km/h |
| August | 30°C | 19°C | 15°C / 40°C | 2 mm | 67% | 8 km/h |
| September | 29°C | 19°C | 8°C / 44°C | 7 mm | 66% | 8 km/h |
| October | 26°C | 16°C | 1°C / 39°C | 93 mm | 64% | 7 km/h |
| November | 23°C | 13°C | 4°C / 34°C | 23 mm | 57% | 8 km/h |
| December | 20°C | 10°C | 2°C / 29°C | 56 mm | 61% | 8 km/h |
Best time to visit Fullerton
The most comfortable time to visit Fullerton is generally April to May and November, balancing mild daytime temperatures against the driest stretch of the year. The city has a moderate seasonal swing and rain concentrates around October, totalling about 372 mm a year.
Travellers who prefer heat should aim for August, when highs average 30°C. October is the month to avoid if rain would spoil your plans — it averages 93 mm, roughly 43× the rainfall of the driest month (August).
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the Fullerton forecast for what is happening now.
Weather across United States right now
- Atlanta30°C
- Austin30°C
- Baltimore28°C
- Boston19°C
- Brooklyn25°C
- Chicago25°C
- Dallas30°C
- Denver30°C
- Detroit20°C
- Houston27°C
- Indianapolis31°C
- Las Vegas33°C
- Los Angeles21°C
- Miami27°C
- Minneapolis27°C
- New York25°C
- Orlando26°C
- Philadelphia25°C
- Phoenix36°C
- Pittsburgh22°C
- Portland15°C
- Queens25°C
- Riverside26°C
- Sacramento21°C
- San Antonio29°C
- San Diego22°C
- San Francisco17°C
- San Jose23°C
- Seattle17°C
- St. Louis32°C
- Tampa25°C
- Washington28°C
