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Monthly climate in Alton, Iowa, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Alton features a humid continental climate (Dfa).Temperatures typically range between -6 °C (21 °F) and 24 °C (76 °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 901 mm (35.5 inches) and receives 96 rainy days on the 1 mm (0.04 inches) threshold annually.Alton enjoys an average of 3044 hours of sunshine throughout the year, and daylight varies from 9 hours 2 minutes to 15 hours 17 minutes per day.

Monthly average temperatures in Alton, Iowa, United States §

The warmest months in Alton are June, July and August, with daily mean temperatures ranging from 22 to 24 °C (72 - 76 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -6 to -3 °C (21 - 27 °F) throughout the day. On average each year, Alton experiences 88 days above 25 °C (77.0 °F) and 138 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Alton, Iowa, 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 11°C
(52°F)		 20°C
(68°F)		 24°C
(76°F)		 29°C
(84°F)		 35°C
(95°F)		 35°C
(95°F)		 35°C
(96°F)		 36°C
(96°F)		 33°C
(92°F)		 31°C
(87°F)		 25°C
(77°F)		 19°C
(66°F)
Mean maximum 9°C
(48°F)		 12°C
(53°F)		 20°C
(69°F)		 26°C
(79°F)		 31°C
(89°F)		 32°C
(90°F)		 34°C
(94°F)		 32°C
(90°F)		 32°C
(91°F)		 28°C
(83°F)		 18°C
(65°F)		 12°C
(54°F)
Average high -1°C
(30°F)		 -1°C
(30°F)		 8°C
(46°F)		 14°C
(57°F)		 21°C
(69°F)		 28°C
(83°F)		 29°C
(84°F)		 27°C
(81°F)		 25°C
(77°F)		 15°C
(59°F)		 7°C
(45°F)		 2°C
(36°F)
Daily mean -6°C
(21°F)		 -6°C
(21°F)		 2°C
(36°F)		 8°C
(46°F)		 15°C
(60°F)		 23°C
(73°F)		 24°C
(76°F)		 22°C
(72°F)		 19°C
(66°F)		 9°C
(49°F)		 2°C
(36°F)		 -3°C
(27°F)
Average low -10°C
(14°F)		 -11°C
(12°F)		 -2°C
(28°F)		 2°C
(36°F)		 10°C
(51°F)		 17°C
(63°F)		 19°C
(66°F)		 17°C
(62°F)		 13°C
(56°F)		 4°C
(40°F)		 -3°C
(27°F)		 -7°C
(20°F)
Mean minimum -23°C
(-9°F)		 -24°C
(-10°F)		 -13°C
(9°F)		 -8°C
(18°F)		 2°C
(36°F)		 10°C
(51°F)		 12°C
(54°F)		 10°C
(51°F)		 5°C
(41°F)		 -5°C
(23°F)		 -13°C
(9°F)		 -17°C
(1°F)
Minimum -29°C
(-20°F)		 -30°C
(-22°F)		 -25°C
(-12°F)		 -14°C
(7°F)		 0°C
(33°F)		 7°C
(45°F)		 11°C
(52°F)		 9°C
(48°F)		 3°C
(38°F)		 -10°C
(14°F)		 -16°C
(4°F)		 -24°C
(-10°F)

Compare climate in Alton with other places

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

Monthly average precipitation in Alton, Iowa, United States §

Alton usually has the most precipitation in May, June and September, with an average of 11 rainy days and 119 mm (4.7 inches) of precipitation per month.The driest months in Alton are January, February and November. On average, 29 mm (1.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Alton, Iowa, 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) 26 (1.0) 32 (1.3) 72 (2.8) 95 (3.7) 140 (5.5) 114 (4.5) 72 (2.8) 100 (3.9) 101 (4.0) 82 (3.2) 28 (1.1) 39 (1.5)
Average precipitation days (≥ 1 mm) 4 7 8 9 15 10 8 9 8 9 5 4

Monthly sunshine hours in Alton, Iowa, United States §

The sunniest months in Alton are June, July and August, when the sun shines an average of 11 hours 21 minutes a day.Least sunny months in Alton: January, November and December receive an average of 6 hours 8 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Alton, Iowa, 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 150 209 221 248 269 348 366 330 261 224 209 204
Mean daily daylight hours 9h 24m 10h 32m 11h 58m 13h 25m 14h 40m 15h 17m 14h 57m 13h 50m 12h 26m 10h 58m 9h 42m 9h 2m

Solar UV radiation in Alton, Iowa, United States §

Alton experiences the highest level of ultraviolet (UV) radiation in June, July and August, when the maximum UV index can reach values of 9 - 11, which corresponds to the Very High / Extreme 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 Alton UV Index data.

Average daily maximum UV levels by month for Alton, Iowa, 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) 2 5 5 8 9 11 10 9 8 5 3 3