S
M
T
W
T
F
S
26
80°
52°
27
80°
62°
28
62°
55°
29
64°
48°
30
66°
42°
1
61°
43°
2
60°
42°
3
76°
54°
4
78°
57°
5
62°
46°
6
56°
42°
7
62°
44°
8
68°
51°
9
70°
52°
10
72°
52°
11
73°
54°
12
71°
54°
13
73°
51°
14
75°
55°
15
73°
59°
16
69°
58°
17
74°
61°
18
77°
61°
19
77°
60°
20
78°
62°
21
78°
62°
22
76°
59°
23
74°
54°
24
72°
56°
25
76°
63°
26
77°
59°
27
73°
57°
28
74°
56°
29
73°
55°
30
75°
63°
31
81°
64°
1
76°
64°
2
83°
65°
3
83°
62°
4
75°
57°
5
75°
57°
6
76°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
May Weather in St. Charles
St. Charles's May 2026 forecast shows daily high temperatures ranging from 56° to 83°, with overnight lows between 42° and 65°. The average high for May is 73° with an average low of 56°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how May weather will actually feel in St. Charles. See also: June | July | August.
