S
M
T
W
T
F
S
30
67°
46°
31
66°
43°
1
65°
44°
2
66°
44°
3
64°
42°
4
64°
46°
5
67°
51°
6
68°
46°
7
71°
41°
8
63°
42°
9
63°
40°
10
62°
43°
11
64°
44°
12
60°
47°
13
67°
47°
14
60°
39°
15
59°
39°
16
Hist. Avg.
61°
40°
17
Hist. Avg.
61°
40°
18
Hist. Avg.
61°
40°
19
Hist. Avg.
60°
40°
20
Hist. Avg.
60°
39°
21
Hist. Avg.
60°
39°
22
Hist. Avg.
59°
39°
23
Hist. Avg.
59°
39°
24
Hist. Avg.
59°
38°
25
Hist. Avg.
59°
38°
26
Hist. Avg.
58°
38°
27
Hist. Avg.
58°
37°
28
Hist. Avg.
58°
37°
29
Hist. Avg.
57°
37°
30
Hist. Avg.
57°
37°
1
Hist. Avg.
57°
36°
2
Hist. Avg.
57°
36°
3
Hist. Avg.
56°
36°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Thunder Bay
Thunder Bay's September 2026 forecast shows daily high temperatures ranging from 59° to 71°, with overnight lows between 39° and 51°. The average high for September is 64° with an average low of 44°. 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 Thunder Bay. See also: October | November | December.
