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Monthly climate in Waterloo, Illinois, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Waterloo features a humid subtropical climate (Cfa).Temperatures typically range between 1 °C (34 °F) and 27 °C (80 °F) through the year, but rarely can drop to -20 °C (-3 °F) or can rise to as high as 39 °C (102 °F).The average annual precipitation amounts to about 1210 mm (47.6 inches) and receives 125 rainy days on the 1 mm (0.04 inches) threshold annually.Waterloo enjoys an average of 2989 hours of sunshine throughout the year, and daylight varies from 9 hours 31 minutes to 14 hours 46 minutes per day.

Monthly average temperatures in Waterloo, Illinois, United States §

The warmest months in Waterloo are June, July and August, with daily mean temperatures ranging from 25 to 27 °C (77 - 80 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 1 to 4 °C (34 - 40 °F) throughout the day. On average each year, Waterloo experiences 124 days above 25 °C (77.0 °F) and 69 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Waterloo, Illinois, 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 20°C
(69°F)		 25°C
(78°F)		 28°C
(83°F)		 31°C
(88°F)		 34°C
(93°F)		 35°C
(96°F)		 39°C
(102°F)		 36°C
(97°F)		 34°C
(94°F)		 34°C
(94°F)		 26°C
(78°F)		 24°C
(76°F)
Mean maximum 17°C
(63°F)		 21°C
(71°F)		 25°C
(78°F)		 29°C
(84°F)		 32°C
(90°F)		 34°C
(93°F)		 36°C
(97°F)		 35°C
(95°F)		 34°C
(93°F)		 32°C
(90°F)		 23°C
(74°F)		 21°C
(70°F)
Average high 5°C
(41°F)		 8°C
(46°F)		 14°C
(58°F)		 19°C
(66°F)		 25°C
(76°F)		 30°C
(86°F)		 31°C
(89°F)		 30°C
(86°F)		 28°C
(83°F)		 21°C
(70°F)		 13°C
(55°F)		 10°C
(50°F)
Daily mean 1°C
(34°F)		 3°C
(37°F)		 9°C
(48°F)		 13°C
(56°F)		 20°C
(68°F)		 25°C
(77°F)		 27°C
(80°F)		 25°C
(77°F)		 22°C
(73°F)		 15°C
(60°F)		 7°C
(45°F)		 4°C
(40°F)
Average low -3°C
(27°F)		 -2°C
(28°F)		 4°C
(40°F)		 8°C
(46°F)		 15°C
(59°F)		 20°C
(68°F)		 22°C
(72°F)		 20°C
(68°F)		 17°C
(63°F)		 10°C
(51°F)		 2°C
(36°F)		 -0°C
(32°F)
Mean minimum -15°C
(5°F)		 -14°C
(7°F)		 -7°C
(19°F)		 -0°C
(32°F)		 7°C
(45°F)		 15°C
(59°F)		 18°C
(64°F)		 15°C
(58°F)		 10°C
(50°F)		 0°C
(33°F)		 -6°C
(21°F)		 -10°C
(15°F)
Minimum -20°C
(-3°F)		 -19°C
(-2°F)		 -16°C
(4°F)		 -4°C
(26°F)		 4°C
(39°F)		 12°C
(54°F)		 16°C
(61°F)		 13°C
(55°F)		 8°C
(46°F)		 -3°C
(28°F)		 -12°C
(11°F)		 -15°C
(4°F)

Compare climate in Waterloo with other places

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

Monthly average precipitation in Waterloo, Illinois, United States §

Waterloo usually has the most precipitation in March, April and May, with an average of 13 rainy days and 143 mm (5.6 inches) of precipitation per month.The driest months in Waterloo are September, November and December. On average, 69 mm (2.7 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Waterloo, Illinois, 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) 79 (3.1) 87 (3.4) 136 (5.4) 142 (5.6) 149 (5.9) 87 (3.4) 89 (3.5) 123 (4.8) 66 (2.6) 109 (4.3) 75 (2.9) 68 (2.7)
Average precipitation days (≥ 1 mm) 8 10 13 12 14 11 11 12 7 11 9 7

Monthly sunshine hours in Waterloo, Illinois, United States §

The sunniest months in Waterloo are June, July and August, when the sun shines an average of 10 hours 55 minutes a day.Least sunny months in Waterloo: January, February and December receive an average of 5 hours 29 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Waterloo, Illinois, 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 127 176 207 239 289 328 348 328 291 242 214 195
Mean daily daylight hours 9h 49m 10h 46m 11h 58m 13h 13m 14h 15m 14h 46m 14h 29m 13h 34m 12h 22m 11h 8m 10h 4m 9h 31m

Solar UV radiation in Waterloo, Illinois, United States §

Waterloo experiences the highest level of ultraviolet (UV) radiation in May, June 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, February 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 Waterloo UV Index data.

Average daily maximum UV levels by month for Waterloo, Illinois, 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 7 9 10 11 10 10 9 7 5 3