S
M
T
W
T
F
S
26
85°
65°
27
83°
66°
28
81°
65°
29
87°
63°
30
81°
67°
31
88°
69°
1
88°
67°
2
82°
64°
3
82°
64°
4
83°
67°
5
81°
68°
6
82°
68°
7
80°
67°
8
81°
67°
9
81°
64°
10
82°
67°
11
85°
66°
12
81°
63°
13
83°
67°
14
87°
68°
15
86°
67°
16
83°
66°
17
83°
64°
18
86°
67°
19
80°
67°
20
84°
66°
21
80°
66°
22
79°
65°
23
78°
65°
24
79°
66°
25
80°
66°
26
81°
65°
27
81°
67°
28
82°
63°
29
87°
65°
30
85°
63°
31
82°
64°
1
84°
64°
2
83°
63°
3
85°
63°
4
84°
62°
5
83°
62°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in Collinsville
Collinsville's August 2026 forecast shows daily high temperatures ranging from 78° to 88°, with overnight lows between 62° and 69°. The average high for August is 83° with an average low of 65°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how August weather will actually feel in Collinsville. See also: September | October | November.
