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Monthly climate in Illiopolis, Illinois, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Illiopolis features a humid continental climate (Dfa).Temperatures typically range between -2 °C (30 °F) and 25 °C (78 °F) through the year, but rarely can drop to -26 °C (-15 °F) or can rise to as high as 35 °C (96 °F).The average annual precipitation amounts to about 1161 mm (45.7 inches) and receives 119 rainy days on the 1 mm (0.04 inches) threshold annually.Illiopolis enjoys an average of 2977 hours of sunshine throughout the year, and daylight varies from 9 hours 24 minutes to 14 hours 54 minutes per day.

Monthly average temperatures in Illiopolis, Illinois, United States §

The warmest months in Illiopolis are June, July and August, with daily mean temperatures ranging from 23 to 25 °C (74 - 78 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -2 to 2 °C (30 - 37 °F) throughout the day. On average each year, Illiopolis experiences 113 days above 25 °C (77.0 °F) and 93 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Illiopolis, 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 17°C
(64°F)		 23°C
(74°F)		 26°C
(78°F)		 29°C
(84°F)		 34°C
(94°F)		 35°C
(95°F)		 35°C
(96°F)		 33°C
(92°F)		 35°C
(95°F)		 33°C
(91°F)		 25°C
(76°F)		 19°C
(67°F)
Mean maximum 15°C
(59°F)		 18°C
(64°F)		 22°C
(71°F)		 28°C
(82°F)		 32°C
(89°F)		 33°C
(92°F)		 34°C
(93°F)		 33°C
(91°F)		 33°C
(91°F)		 31°C
(88°F)		 20°C
(69°F)		 18°C
(64°F)
Average high 3°C
(37°F)		 5°C
(41°F)		 12°C
(53°F)		 17°C
(63°F)		 24°C
(75°F)		 29°C
(84°F)		 30°C
(86°F)		 28°C
(83°F)		 27°C
(82°F)		 20°C
(68°F)		 10°C
(51°F)		 7°C
(45°F)
Daily mean -2°C
(30°F)		 0°C
(32°F)		 6°C
(44°F)		 11°C
(53°F)		 19°C
(66°F)		 24°C
(75°F)		 25°C
(78°F)		 23°C
(74°F)		 22°C
(71°F)		 14°C
(58°F)		 5°C
(42°F)		 2°C
(37°F)
Average low -6°C
(22°F)		 -5°C
(24°F)		 2°C
(35°F)		 6°C
(43°F)		 14°C
(57°F)		 19°C
(66°F)		 20°C
(69°F)		 18°C
(65°F)		 16°C
(61°F)		 9°C
(49°F)		 1°C
(34°F)		 -2°C
(28°F)
Mean minimum -19°C
(-2°F)		 -18°C
(0°F)		 -10°C
(14°F)		 -2°C
(28°F)		 4°C
(40°F)		 14°C
(57°F)		 15°C
(59°F)		 12°C
(54°F)		 8°C
(47°F)		 -1°C
(31°F)		 -8°C
(18°F)		 -12°C
(11°F)
Minimum -26°C
(-15°F)		 -22°C
(-7°F)		 -18°C
(1°F)		 -7°C
(20°F)		 0°C
(33°F)		 10°C
(51°F)		 13°C
(56°F)		 11°C
(52°F)		 6°C
(42°F)		 -4°C
(24°F)		 -13°C
(9°F)		 -19°C
(-3°F)

Compare climate in Illiopolis with other places

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

Monthly average precipitation in Illiopolis, Illinois, United States §

Illiopolis usually has the most precipitation in March, April and May, with an average of 12 rainy days and 135 mm (5.3 inches) of precipitation per month.The driest months in Illiopolis are January, September and December. On average, 61 mm (2.4 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Illiopolis, 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) 72 (2.8) 74 (2.9) 130 (5.1) 130 (5.1) 145 (5.7) 111 (4.4) 115 (4.5) 91 (3.6) 61 (2.4) 109 (4.3) 72 (2.8) 51 (2.0)
Average precipitation days (≥ 1 mm) 8 10 12 11 14 10 11 10 7 10 9 7

Monthly sunshine hours in Illiopolis, Illinois, United States §

The sunniest months in Illiopolis are June, July and August, when the sun shines an average of 11 hours 6 minutes a day.Least sunny months in Illiopolis: January, February and December receive an average of 5 hours 16 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Illiopolis, 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 118 168 210 242 287 339 352 330 293 236 203 193
Mean daily daylight hours 9h 42m 10h 42m 11h 58m 13h 16m 14h 22m 14h 54m 14h 36m 13h 38m 12h 23m 11h 6m 9h 58m 9h 24m

Solar UV radiation in Illiopolis, Illinois, United States §

Illiopolis experiences the highest level of ultraviolet (UV) radiation in May, 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 4. For more detailed information, check out our hourly Illiopolis UV Index data.

Average daily maximum UV levels by month for Illiopolis, 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 6 9 10 11 11 9 8 6 4 3