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
73°
67°
16
74°
60°
17
74°
59°
18
72°
52°
19
66°
58°
20
68°
58°
21
67°
58°
22
66°
54°
23
69°
53°
24
70°
55°
25
68°
56°
26
67°
54°
27
69°
56°
28
67°
50°
29
69°
55°
30
67°
55°
1
70°
56°
2
72°
54°
3
68°
54°
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 66° to 74°, with overnight lows between 50° and 67°. The average high for September is 69° 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 September weather will actually feel in St. Catharines. See also: October | November | December.
