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Monthly climate in Ontario, California, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Ontario features a warm-summer Mediterranean climate (Csb).Temperatures typically range between 12 °C (54 °F) and 25 °C (77 °F) through the year, but rarely can drop to 1 °C (34 °F) or can rise to as high as 44 °C (111 °F).The average annual precipitation amounts to about 394 mm (15.5 inches) and receives 34 rainy days on the 1 mm (0.04 inches) threshold annually.Ontario enjoys an average of 3575 hours of sunshine throughout the year, and daylight varies from 9 hours 54 minutes to 14 hours 22 minutes per day.

Monthly average temperatures in Ontario, California, United States §

The warmest months in Ontario are July, August and September, with daily mean temperatures ranging from 23 to 25 °C (74 - 77 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 12 to 12 °C (54 - 55 °F) throughout the day. On average each year, Ontario experiences 143 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 Ontario, 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 30°C
(86°F)		 29°C
(84°F)		 30°C
(86°F)		 35°C
(95°F)		 33°C
(91°F)		 36°C
(98°F)		 43°C
(110°F)		 39°C
(102°F)		 44°C
(111°F)		 38°C
(101°F)		 33°C
(91°F)		 27°C
(81°F)
Mean maximum 25°C
(78°F)		 25°C
(77°F)		 27°C
(82°F)		 32°C
(90°F)		 31°C
(88°F)		 33°C
(92°F)		 37°C
(99°F)		 36°C
(98°F)		 38°C
(100°F)		 35°C
(95°F)		 31°C
(89°F)		 25°C
(77°F)
Average high 18°C
(65°F)		 18°C
(65°F)		 19°C
(67°F)		 23°C
(73°F)		 23°C
(74°F)		 27°C
(81°F)		 31°C
(88°F)		 32°C
(89°F)		 30°C
(86°F)		 27°C
(81°F)		 23°C
(74°F)		 18°C
(65°F)
Daily mean 12°C
(54°F)		 12°C
(55°F)		 14°C
(57°F)		 16°C
(62°F)		 18°C
(64°F)		 21°C
(70°F)		 24°C
(76°F)		 25°C
(77°F)		 23°C
(74°F)		 20°C
(68°F)		 16°C
(61°F)		 12°C
(54°F)
Average low 8°C
(46°F)		 8°C
(46°F)		 9°C
(48°F)		 12°C
(53°F)		 13°C
(56°F)		 16°C
(61°F)		 19°C
(66°F)		 19°C
(67°F)		 18°C
(64°F)		 14°C
(58°F)		 11°C
(52°F)		 8°C
(46°F)
Mean minimum 3°C
(38°F)		 2°C
(37°F)		 4°C
(39°F)		 8°C
(46°F)		 9°C
(48°F)		 12°C
(55°F)		 16°C
(61°F)		 16°C
(61°F)		 14°C
(57°F)		 9°C
(49°F)		 7°C
(45°F)		 3°C
(37°F)
Minimum 2°C
(36°F)		 1°C
(34°F)		 3°C
(37°F)		 7°C
(44°F)		 6°C
(44°F)		 11°C
(52°F)		 14°C
(58°F)		 15°C
(60°F)		 12°C
(53°F)		 8°C
(47°F)		 4°C
(40°F)		 2°C
(36°F)

Compare climate in Ontario with other places

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

Monthly average precipitation in Ontario, California, United States §

Ontario usually has the most precipitation in January, March and December, with an average of 6 rainy days and 78 mm (3.1 inches) of precipitation per month.The driest months in Ontario are June, July and August. On average, 1 mm (0.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Ontario, 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) 80 (3.1) 70 (2.8) 76 (3.0) 27 (1.1) 17 (0.7) 1 (0.0) 1 (0.1) 2 (0.1) 3 (0.1) 12 (0.5) 26 (1.0) 79 (3.1)
Average precipitation days (≥ 1 mm) 5 6 9 3 3 0 0 0 0 1 2 5

Monthly sunshine hours in Ontario, California, United States §

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

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Ontario, 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 185 232 281 318 354 373 380 361 318 293 254 221
Mean daily daylight hours 10h 9m 10h 58m 11h 59m 13h 3m 13h 56m 14h 22m 14h 7m 13h 20m 12h 20m 11h 17m 10h 22m 9h 54m

Solar UV radiation in Ontario, California, United States §

Ontario experiences the highest level of ultraviolet (UV) radiation in April, June and July, when the maximum UV index can reach values of 10 - 12, 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 Ontario UV Index data.

Average daily maximum UV levels by month for Ontario, 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 12 11 10 10 7 5 4