S
M
T
W
T
F
S
30
71°
67°
31
74°
67°
1
79°
71°
2
82°
69°
3
80°
68°
4
76°
67°
5
76°
67°
6
70°
61°
7
76°
60°
8
74°
63°
9
76°
68°
10
80°
66°
11
72°
62°
12
77°
60°
13
81°
64°
14
71°
60°
15
76°
59°
16
74°
68°
17
73°
67°
18
70°
53°
19
68°
55°
20
68°
53°
21
62°
51°
22
61°
51°
23
61°
51°
24
67°
55°
25
65°
54°
26
66°
52°
27
66°
53°
28
67°
54°
29
69°
55°
30
69°
54°
1
70°
49°
2
64°
54°
3
62°
53°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in St. Catharines
St. Catharines's September 2026 forecast shows daily high temperatures ranging from 61° to 70°, with overnight lows between 49° and 55°. The average high for September is 66° with an average low of 53°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in St. Catharines. See also: October | November | December.
