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Monthly climate in Foster City, California, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Foster City features a warm-summer Mediterranean climate (Csb).Temperatures typically range between 11 °C (52 °F) and 18 °C (66 °F) through the year, but rarely can drop to 2 °C (36 °F) or can rise to as high as 39 °C (103 °F).The average annual precipitation amounts to about 511 mm (20.1 inches) and receives 48 rainy days on the 1 mm (0.04 inches) threshold annually.Foster City enjoys an average of 3285 hours of sunshine throughout the year, and daylight varies from 9 hours 36 minutes to 14 hours 41 minutes per day.

Monthly average temperatures in Foster City, California, United States §

The warmest months in Foster City are July, August and September, with daily mean temperatures ranging from 17 to 18 °C (63 - 66 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 11 to 11 °C (52 - 53 °F) throughout the day. On average each year, Foster City experiences 31 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 Foster City, 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 24°C
(75°F)		 24°C
(76°F)		 25°C
(78°F)		 30°C
(87°F)		 29°C
(84°F)		 35°C
(96°F)		 29°C
(84°F)		 35°C
(96°F)		 39°C
(103°F)		 33°C
(92°F)		 27°C
(80°F)		 22°C
(72°F)
Mean maximum 19°C
(66°F)		 21°C
(71°F)		 24°C
(75°F)		 26°C
(79°F)		 26°C
(79°F)		 29°C
(85°F)		 27°C
(81°F)		 31°C
(87°F)		 34°C
(93°F)		 30°C
(87°F)		 24°C
(75°F)		 19°C
(67°F)
Average high 14°C
(58°F)		 16°C
(61°F)		 16°C
(62°F)		 18°C
(64°F)		 19°C
(67°F)		 22°C
(71°F)		 22°C
(72°F)		 23°C
(74°F)		 24°C
(76°F)		 23°C
(73°F)		 18°C
(65°F)		 14°C
(58°F)
Daily mean 11°C
(52°F)		 11°C
(53°F)		 12°C
(54°F)		 13°C
(57°F)		 15°C
(59°F)		 17°C
(63°F)		 17°C
(63°F)		 18°C
(65°F)		 18°C
(66°F)		 17°C
(63°F)		 13°C
(56°F)		 11°C
(52°F)
Average low 8°C
(47°F)		 8°C
(46°F)		 9°C
(48°F)		 10°C
(50°F)		 11°C
(52°F)		 13°C
(56°F)		 13°C
(57°F)		 15°C
(59°F)		 14°C
(58°F)		 12°C
(55°F)		 10°C
(50°F)		 8°C
(46°F)
Mean minimum 4°C
(39°F)		 4°C
(39°F)		 5°C
(41°F)		 7°C
(44°F)		 9°C
(48°F)		 11°C
(51°F)		 12°C
(54°F)		 13°C
(55°F)		 11°C
(52°F)		 8°C
(48°F)		 6°C
(43°F)		 4°C
(39°F)
Minimum 2°C
(36°F)		 2°C
(37°F)		 4°C
(40°F)		 6°C
(42°F)		 8°C
(46°F)		 10°C
(49°F)		 11°C
(53°F)		 12°C
(54°F)		 10°C
(50°F)		 7°C
(45°F)		 4°C
(39°F)		 3°C
(37°F)

Compare climate in Foster City with other places

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

Monthly average precipitation in Foster City, California, United States §

Foster City usually has the most precipitation in January, February and December, with an average of 8 rainy days and 98 mm (3.8 inches) of precipitation per month.The driest months in Foster City are July, August and September. On average, 1 mm (0.0 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Foster City, 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) 105 (4.1) 100 (3.9) 86 (3.4) 33 (1.3) 24 (0.9) 2 (0.1) 0 (0.0) 0 (0.0) 2 (0.1) 24 (0.9) 47 (1.9) 88 (3.5)
Average precipitation days (≥ 1 mm) 7 8 11 5 2 0 0 0 0 1 5 9

Monthly sunshine hours in Foster City, California, United States §

The sunniest months in Foster City are May, June and July, when the sun shines an average of 11 hours 22 minutes a day.Least sunny months in Foster City: January, February and December receive an average of 6 hours 10 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Foster City, 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 151 215 262 296 341 355 349 319 298 275 224 194
Mean daily daylight hours 9h 54m 10h 49m 11h 59m 13h 11m 14h 11m 14h 41m 14h 25m 13h 31m 12h 22m 11h 10m 10h 8m 9h 36m

Solar UV radiation in Foster City, California, United States §

Foster City experiences the highest level of ultraviolet (UV) radiation in June, July and August, 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 4. For more detailed information, check out our hourly Foster City UV Index data.

Average daily maximum UV levels by month for Foster City, 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) 3 5 8 9 10 11 11 10 9 7 4 3