S
M
T
W
T
F
S
30
71°
67°
31
74°
67°
1
79°
71°
2
82°
69°
3
80°
68°
4
75°
63°
5
75°
61°
6
72°
55°
7
76°
59°
8
76°
64°
9
81°
65°
10
75°
55°
11
71°
59°
12
76°
62°
13
75°
61°
14
73°
59°
15
74°
57°
16
73°
58°
17
74°
53°
18
68°
54°
19
72°
56°
20
76°
59°
21
76°
59°
22
75°
57°
23
74°
56°
24
69°
56°
25
74°
57°
26
72°
56°
27
71°
53°
28
63°
53°
29
62°
52°
30
62°
50°
1
61°
49°
2
61°
54°
3
67°
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 81°, with overnight lows between 49° and 65°. The average high for September is 72° with an average low of 57°. 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.
