Illiopolis climate

Illiopolis Weather in August

NOAA 1991-2020 normals for Decatur Wtp, 25 km from Illiopolis

Average highs run from 84°F on August 1 to 82°F on August 31, and lows from 66°F to 62°F. Normal precipitation for the month is 3.50 in over about 7 wet days.

August day by day

The normal high and low for each date, and the record, in °F.

Normal daily high and low temperature at Illiopolis, in °F, with the record for each date.406080100120151015202530
  • Normal low
  • Normal high
  • Record high
  • Record low

August at a glance

Average high
84°F
Average low
65°F
Precipitation
3.50 in
Record high
100°FAug 12, 2007
Record low
46°FAug 16, 2004
Chance of a freeze
0%
Days of 90°F or more
6.9
Daylight
14 h 14 min to 13 h 06 min
Cloud cover
49%
Humidity
73%
Dew point
64°F
Wind
7.4 mph

Every day of the month

A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.

DateNormal highNormal lowRecord highRecord lowChance wetChance of snow
Aug 184°F66°F98°F 200653°F 201927%0%
Aug 284°F66°F99°F 201256°F 201426%0%
Aug 384°F66°F96°F 201054°F 202526%0%
Aug 484°F66°F96°F 201056°F 201326%0%
Aug 584°F66°F94°F 200751°F 202026%0%
Aug 684°F66°F92°F 200651°F 200426%0%
Aug 784°F66°F97°F 200749°F 200426%0%
Aug 884°F66°F95°F 201251°F 200425%0%
Aug 984°F66°F96°F 201054°F 200225%0%
Aug 1084°F66°F97°F 201056°F 200325%0%
Aug 1184°F66°F95°F 200551°F 200825%0%
Aug 1284°F66°F100°F 200751°F 200425%0%
Aug 1384°F66°F96°F 201051°F 200425%0%
Aug 1484°F65°F95°F 200748°F 201325%0%
Aug 1584°F65°F96°F 200747°F 200425%0%
Aug 1684°F65°F96°F 202546°F 200425%0%
Aug 1784°F65°F90°F 200355°F 201325%0%
Aug 1884°F65°F93°F 202551°F 201225%0%
Aug 1984°F65°F92°F 201052°F 202025%0%
Aug 2083°F65°F93°F 201052°F 202025%0%
Aug 2183°F65°F97°F 200352°F 202425%0%
Aug 2283°F64°F96°F 200749°F 202425%0%
Aug 2383°F64°F98°F 200751°F 202425%0%
Aug 2483°F64°F99°F 202353°F 200925%0%
Aug 2583°F64°F98°F 202352°F 201725%0%
Aug 2683°F64°F96°F 200351°F 201525%0%
Aug 2783°F63°F95°F 202450°F 201525%0%
Aug 2882°F63°F98°F 200753°F 200725%0%
Aug 2982°F63°F99°F 200753°F 200425%0%
Aug 3082°F63°F96°F 201349°F 200425%0%
Aug 3182°F62°F98°F 201347°F 200925%0%

Chance of rain

The chance of at least 0.01 inch of precipitation on each date at Illiopolis, in percent, and of at least 0.1 inch of snowfall.01020301102030
  • Chance of a wet day
  • Chance of snowfall

Sunrise and sunset

Times for 2026, local time (CDT).

August 1
sunrise 5:56 AM, sunset 8:10 PM
August 31
sunrise 6:24 AM, sunset 7:30 PM

Every day of August: sun and moon

Other months

Sources

Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00112193 (Decatur Wtp), public domain. Records: NOAA GHCN-Daily, station USW00003887, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.