Waterloo, IL Weather Forecast & Alerts

Current conditions, 5-day forecast, and active NWS weather alerts for Waterloo, IL.

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Current Conditions — Waterloo, IL

CAHOKIA/ST LOUIS (KCPS)

Clear

55.4 F
Humidity:77%
Wind Speed: 5.7 mph
Barometer:30.06 in
Dewpoint:48.2 F
Visibility:10.00 mi
Precip:--
Heat Index:NA
Wind Chill:NA
Apr 22 2026, 06:35 AM CDT
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5-Day Forecast — Waterloo, IL

Wednesday

High 78 °F
Partly Sunny
Wednesday
Night
Low 55 °F
Mostly Clear
Thursday

High 80 °F
Partly Sunny
Thursday
Night
Low 62 °F
Chance of T-storms
Friday

High 75 °F
T-storms
Friday
Night
Low 57 °F
Chance of Rain
Saturday

High 75 °F
Partly Sunny
Saturday
Night
Low 53 °F
Slight Chance of Showers
Sunday

High 75 °F
Isolated T-storm

Detailed Forecast — Waterloo, IL

Wednesday
Partly Sunny. High near 78°F. Wind 6 to 9 mph, with gusts as high as 15 mph.
Wednesday Night
Mostly Clear. Low around 55°F. Wind 6 to 7 mph, with gusts as high as 13 mph.
Thursday
Partly Sunny. High near 80°F. Wind 9 to 16 mph, with gusts as high as 26 mph.
Thursday Night
Chance of Thunderstorms. Low around 62°F. Wind around 13 mph, with gusts as high as 22 mph.
Friday
Thunderstorms. High near 75°F. Wind 6 to 13 mph, with gusts as high as 20 mph.
Friday Night
Chance of Rain. Low around 57°F. Wind around 5 mph, with gusts as high as 9 mph.
Saturday
Partly Sunny. High near 75°F. Wind 5 to 8 mph, with gusts as high as 13 mph.
Saturday Night
Slight Chance of Showers. Low around 53°F. Wind around 5 mph, with gusts as high as 10 mph.
Sunday
Isolated T-storm. High near 75°F. Wind around 10 mph, with gusts as high as 17 mph.
Sunday Night
Chance of Thunderstorms. Low around 59°F. Wind around 12 mph, with gusts as high as 20 mph.
Monday
Thunderstorms Likely. High near 77°F. Wind 13 to 14 mph, with gusts as high as 23 mph.
Monday Night
Chance of Showers. Low around 53°F. Wind around 10 mph, with gusts as high as 18 mph.
Tuesday
Partly Sunny. High near 71°F. Wind 7 to 12 mph, with gusts as high as 18 mph.
IL Radar
Current Radar • IL
Day 1 Outlook • April 22, 2026

Observation History — Waterloo, IL

Time Wind
(mph)		 Vis
(mi)		 Weather Precip (in) Temperature (F) Relative
Humidity		 Wind
Chill
(F)		 Heat
Index
(F)		 Pressure
Air Dwpt altimeter
(in)		 sea level
(mb)
06:35 AM CDT 5.7 10.00 Clear -- 55.4 48.2 77% NA NA 30.06 1017.9
06:30 AM CDT SW 5.7 10.00 Clear -- 55.4 48.2 77% NA NA 30.06 1017.9
06:20 AM CDT 6.9 10.00 Clear -- 53.6 48.2 82% NA NA 30.06 1017.9
06:05 AM CDT SW 5.7 10.00 Clear -- 55.4 48.2 77% NA NA 30.06 1017.9
06:00 AM CDT 0.0 10.00 Clear -- 55.4 48.2 77% NA NA 30.06 1017.9
05:50 AM CDT 0.0 10.00 Clear -- 57.2 48.2 72% NA NA 30.06 1017.9
05:35 AM CDT 0.0 10.00 Clear -- 60.8 48.2 63% NA NA 30.05 1017.6
05:20 AM CDT 0.0 10.00 Clear -- 60.8 48.2 63% NA NA 30.05 1017.6
05:00 AM CDT SW 4.6 10.00 Clear -- 62.6 48.2 59% NA NA 30.05 1017.6
04:50 AM CDT SW 5.7 10.00 Clear -- 62.6 48.2 59% NA NA 30.05 1017.6
04:45 AM CDT SW 5.7 10.00 Clear -- 62.6 48.2 59% NA NA 30.05 1017.6
04:30 AM CDT SW 6.9 10.00 Clear -- 62.6 48.2 59% NA NA 30.05 1017.6
04:25 AM CDT SW 4.6 10.00 Clear -- 62.6 48.2 59% NA NA 30.05 1017.6
04:20 AM CDT SW 4.6 10.00 Clear -- 62.6 50.0 63% NA NA 30.05 1017.6
04:15 AM CDT SW 4.6 10.00 Clear -- 62.6 50.0 63% NA NA 30.05 1017.6
04:10 AM CDT SW 4.6 10.00 Clear -- 62.6 50.0 63% NA NA 30.05 1017.6
04:00 AM CDT SW 4.6 10.00 Clear -- 62.6 50.0 63% NA NA 30.04 1017.3
03:45 AM CDT 3.4 10.00 Clear -- 62.6 50.0 63% NA NA 30.04 1017.3
03:40 AM CDT 3.4 10.00 Clear -- 62.6 50.0 63% NA NA 30.04 1017.3
03:35 AM CDT 4.6 10.00 Clear -- 64.4 50.0 60% NA NA 30.04 1017.3
03:20 AM CDT SW 3.4 10.00 Clear -- 64.4 48.2 56% NA NA 30.04 1017.3
03:15 AM CDT SW 3.4 10.00 Clear -- 64.4 48.2 56% NA NA 30.04 1017.3
03:00 AM CDT 4.6 10.00 Clear -- 64.4 48.2 56% NA NA 30.04 1017.3
02:50 AM CDT SW 4.6 10.00 Clear -- 64.4 48.2 56% NA NA 30.04 1017.3

Regional Weather Observation

CAHOKIA/ST LOUIS (KCPS)

Clear
55.4 F

ST LOUIS (KSTL)

Clear
60.8 F

ST LOUIS/SPIRIT (KSUS)

Clear
59.0 F

ALTON/ST LOUIS R (KALN)

Clear
59.5 F

ST CHARLES (KSET)

Clear
57.2 F

SCOTT AFB/BELLEV (KBLV)

Clear
54.5 F
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