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Monthly climate in Cornwall, Ontario, Canada

Last updated: March 2, 2024

Under the Köppen–Geiger climate classification Cornwall features a humid continental climate (Dfb). Temperatures typically range between -7 °C (20 °F) and 22 °C (72 °F) through the year, but rarely can drop to -30 °C (-22 °F) or can rise to as high as 36 °C (96 °F). The average annual precipitation amounts to about 1198 mm (47.2 inches) and receives 151 rainy days on the 1 mm (0.04 inches) threshold annually. Cornwall enjoys an average of 2759 hours of sunshine throughout the year, and daylight varies from 8 hours 48 minutes to 15 hours 32 minutes per day.

Monthly average temperatures in Cornwall, Ontario, Canada §

The warmest months in Cornwall are June, July and August, with daily mean temperatures ranging from 19 to 22 °C (66 - 72 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -7 to -3 °C (20 - 26 °F) throughout the day. On average each year, Cornwall experiences 59 days above 25 °C (77.0 °F) and 130 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Cornwall, Ontario, Canada. 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 14°C
(57°F)		 16°C
(60°F)		 22°C
(72°F)		 28°C
(83°F)		 35°C
(96°F)		 34°C
(93°F)		 36°C
(96°F)		 33°C
(91°F)		 32°C
(90°F)		 27°C
(81°F)		 23°C
(74°F)		 16°C
(62°F)
Mean maximum 7°C
(45°F)		 10°C
(50°F)		 15°C
(59°F)		 23°C
(73°F)		 31°C
(87°F)		 30°C
(87°F)		 33°C
(91°F)		 31°C
(88°F)		 29°C
(85°F)		 25°C
(77°F)		 17°C
(63°F)		 12°C
(53°F)
Average high -3°C
(26°F)		 -1°C
(30°F)		 3°C
(38°F)		 11°C
(53°F)		 19°C
(67°F)		 24°C
(75°F)		 27°C
(81°F)		 26°C
(79°F)		 22°C
(71°F)		 15°C
(59°F)		 5°C
(42°F)		 -0°C
(32°F)
Daily mean -7°C
(20°F)		 -6°C
(22°F)		 -1°C
(30°F)		 6°C
(44°F)		 14°C
(57°F)		 19°C
(66°F)		 22°C
(72°F)		 21°C
(70°F)		 16°C
(62°F)		 10°C
(51°F)		 2°C
(36°F)		 -3°C
(26°F)
Average low -11°C
(12°F)		 -10°C
(14°F)		 -6°C
(22°F)		 2°C
(36°F)		 8°C
(47°F)		 13°C
(56°F)		 17°C
(62°F)		 16°C
(61°F)		 12°C
(53°F)		 6°C
(43°F)		 -2°C
(29°F)		 -7°C
(20°F)
Mean minimum -25°C
(-12°F)		 -22°C
(-8°F)		 -18°C
(-1°F)		 -5°C
(24°F)		 0°C
(33°F)		 7°C
(45°F)		 10°C
(51°F)		 9°C
(49°F)		 5°C
(40°F)		 -2°C
(29°F)		 -13°C
(9°F)		 -20°C
(-3°F)
Minimum -30°C
(-22°F)		 -25°C
(-13°F)		 -20°C
(-4°F)		 -9°C
(15°F)		 -1°C
(30°F)		 3°C
(37°F)		 9°C
(48°F)		 8°C
(47°F)		 -0°C
(32°F)		 -4°C
(25°F)		 -18°C
(1°F)		 -28°C
(-19°F)

Compare climate in Cornwall with other places

Compare temperature, precipitation, sunshine, UV index in Cornwall, Ontario, Canada with other places around the world.

Monthly average precipitation in Cornwall, Ontario, Canada §

Cornwall usually has the most precipitation in April, July and October, with an average of 13 rainy days and 124 mm (4.9 inches) of precipitation per month. The driest months in Cornwall are February, September and December. On average, 79 mm (3.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Cornwall, Ontario, Canada. 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) 85 (3.3) 83 (3.3) 87 (3.4) 117 (4.6) 109 (4.3) 100 (3.9) 116 (4.6) 100 (3.9) 70 (2.8) 139 (5.5) 108 (4.2) 84 (3.3)
Average precipitation days (≥ 1 mm) 11 13 12 13 13 12 14 14 9 14 14 12

Monthly sunshine hours in Cornwall, Ontario, Canada §

The sunniest months in Cornwall are June, July and August, when the sun shines an average of 10 hours 44 minutes a day. Least sunny months in Cornwall: January, November and December receive an average of 4 hours 20 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Cornwall, Ontario, Canada. 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 116 151 233 226 282 317 347 323 279 197 149 134
Mean daily daylight hours 9h 12m 10h 25m 11h 57m 13h 31m 14h 52m 15h 32m 15h 10m 13h 58m 12h 27m 10h 54m 9h 31m 8h 48m

Solar UV radiation in Cornwall, Ontario, Canada §

Cornwall experiences the highest level of ultraviolet (UV) radiation in May, June and July, when the maximum UV index can reach values of 9 - 9, which corresponds to the Very High category of sun exposure. January, November and December are in the Low / Moderate exposure category. In these months, the maximum values of the UV index do not exceed 3. For more detailed information, check out our hourly Cornwall UV Index data.

Average daily maximum UV levels by month for Cornwall, Ontario, Canada. 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) 2 4 5 8 9 9 9 8 7 5 3 2

Detailed Monthly Weather Insights for Cornwall, Ontario, Canada

Discover in-depth weather details for every month in Cornwall. Click through the links below for comprehensive overviews of temperature trends, precipitation levels, sunshine hours, and solar UV radiation specifics. Whether planning a visit or simply curious about Cornwall's climate nuances, these monthly breakdowns provide the information you need for an informed understanding of what to expect throughout the year.

Each link leads to a detailed account of the typical weather conditions for that month, providing both locals and tourists with vital information to plan their daily activities, wardrobe, and travel itineraries accordingly.