S
M
T
W
T
F
S
30
72°
57°
31
65°
61°
1
82°
57°
2
78°
52°
3
74°
49°
4
69°
58°
5
77°
51°
6
77°
48°
7
69°
56°
8
71°
63°
9
72°
52°
10
69°
43°
11
80°
47°
12
69°
53°
13
64°
40°
14
65°
34°
15
68°
43°
16
64°
39°
17
69°
40°
18
57°
34°
19
68°
38°
20
62°
34°
21
60°
30°
22
N/A
23
64°
38°
24
62°
38°
25
N/A
26
64°
46°
27
63°
47°
28
N/A
29
66°
54°
30
77°
48°
1
67°
45°
2
60°
31°
3
55°
29°
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 ° to °, with overnight lows between ° and °. The average high for September is ° with an average low of °. 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.
