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Monthly climate in Fullerton, California, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Fullerton features a cold semi-arid climate (BSk).Temperatures typically range between 14 °C (57 °F) and 23 °C (73 °F) through the year, but rarely can drop to 4 °C (40 °F) or can rise to as high as 39 °C (103 °F).The average annual precipitation amounts to about 314 mm (12.4 inches) and receives 32 rainy days on the 1 mm (0.04 inches) threshold annually.Fullerton enjoys an average of 3581 hours of sunshine throughout the year, and daylight varies from 9 hours 56 minutes to 14 hours 20 minutes per day.

Monthly average temperatures in Fullerton, California, United States §

The warmest months in Fullerton are July, August and September, with daily mean temperatures ranging from 22 to 23 °C (72 - 73 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 14 to 14 °C (57 - 58 °F) throughout the day. On average each year, Fullerton experiences 96 days above 25 °C (77.0 °F) and 0 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Fullerton, California, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to June 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum 29°C
(85°F)		 30°C
(85°F)		 27°C
(81°F)		 34°C
(94°F)		 30°C
(86°F)		 33°C
(91°F)		 39°C
(103°F)		 34°C
(94°F)		 38°C
(102°F)		 38°C
(101°F)		 32°C
(90°F)		 27°C
(82°F)
Mean maximum 26°C
(79°F)		 25°C
(77°F)		 26°C
(79°F)		 30°C
(86°F)		 28°C
(83°F)		 29°C
(85°F)		 33°C
(91°F)		 32°C
(89°F)		 33°C
(93°F)		 34°C
(94°F)		 31°C
(88°F)		 24°C
(76°F)
Average high 19°C
(66°F)		 19°C
(66°F)		 19°C
(67°F)		 21°C
(71°F)		 21°C
(71°F)		 24°C
(75°F)		 27°C
(80°F)		 27°C
(82°F)		 27°C
(81°F)		 26°C
(78°F)		 22°C
(73°F)		 19°C
(66°F)
Daily mean 14°C
(57°F)		 14°C
(58°F)		 15°C
(60°F)		 17°C
(63°F)		 18°C
(64°F)		 20°C
(68°F)		 22°C
(72°F)		 23°C
(73°F)		 22°C
(72°F)		 20°C
(69°F)		 17°C
(63°F)		 14°C
(58°F)
Average low 10°C
(50°F)		 10°C
(50°F)		 11°C
(53°F)		 14°C
(57°F)		 15°C
(59°F)		 16°C
(62°F)		 19°C
(66°F)		 19°C
(67°F)		 19°C
(66°F)		 16°C
(62°F)		 13°C
(56°F)		 10°C
(51°F)
Mean minimum 6°C
(44°F)		 6°C
(43°F)		 8°C
(46°F)		 11°C
(52°F)		 12°C
(54°F)		 15°C
(59°F)		 17°C
(62°F)		 17°C
(63°F)		 16°C
(61°F)		 12°C
(54°F)		 9°C
(49°F)		 6°C
(43°F)
Minimum 5°C
(41°F)		 4°C
(40°F)		 7°C
(44°F)		 10°C
(51°F)		 11°C
(52°F)		 14°C
(57°F)		 16°C
(61°F)		 15°C
(60°F)		 15°C
(58°F)		 11°C
(52°F)		 8°C
(46°F)		 5°C
(42°F)

Compare climate in Fullerton with other places

Compare temperature, precipitation, sunshine, UV index in Fullerton, California, United States with other places around the world.

Monthly average precipitation in Fullerton, California, United States §

Fullerton usually has the most precipitation in January, March and December, with an average of 6 rainy days and 63 mm (2.5 inches) of precipitation per month.The driest months in Fullerton are July, August and September. On average, 3 mm (0.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Fullerton, California, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average precipitation mm (inches) 65 (2.5) 52 (2.0) 55 (2.2) 23 (0.9) 12 (0.5) 4 (0.2) 3 (0.1) 2 (0.1) 3 (0.1) 9 (0.4) 18 (0.7) 68 (2.7)
Average precipitation days (≥ 1 mm) 5 5 8 2 3 0 0 0 0 2 2 5

Monthly sunshine hours in Fullerton, California, United States §

The sunniest months in Fullerton are June, July and August, when the sun shines an average of 12 hours 1 minutes a day.Least sunny months in Fullerton: January, February and December receive an average of 7 hours 9 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Fullerton, California, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean monthly sunshine hours 189 235 290 318 350 366 379 360 316 292 256 226
Mean daily daylight hours 10h 11m 10h 58m 11h 59m 13h 2m 13h 55m 14h 20m 14h 6m 13h 20m 12h 19m 11h 17m 10h 23m 9h 56m

Solar UV radiation in Fullerton, California, United States §

Fullerton experiences the highest level of ultraviolet (UV) radiation in April, June and July, when the maximum UV index can reach values of 10 - 11, which corresponds to the Very High / Extreme category of sun exposure.January, November and December are in the Moderate exposure category. In these months, the maximum values of the UV index do not exceed 5. For more detailed information, check out our hourly Fullerton UV Index data.

Average daily maximum UV levels by month for Fullerton, California, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2022 to January 2023.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
UV Index (month maximum) 4 6 8 10 10 11 11 10 10 7 5 4