S
M
T
W
T
F
S
26
71°
54°
27
78°
55°
28
78°
51°
29
75°
49°
30
76°
48°
31
71°
47°
1
70°
48°
2
68°
47°
3
71°
46°
4
72°
52°
5
75°
53°
6
73°
54°
7
74°
55°
8
71°
53°
9
71°
53°
10
74°
52°
11
73°
50°
12
70°
51°
13
73°
45°
14
70°
47°
15
70°
51°
16
74°
45°
17
72°
43°
18
68°
49°
19
70°
48°
20
73°
47°
21
69°
48°
22
69°
48°
23
74°
46°
24
72°
44°
25
67°
45°
26
67°
45°
27
65°
46°
28
66°
45°
29
64°
45°
30
67°
46°
31
66°
43°
1
65°
44°
2
66°
44°
3
64°
42°
4
64°
46°
5
67°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
August Weather in Thunder Bay
Thunder Bay's August 2026 forecast shows daily high temperatures ranging from 64° to 78°, with overnight lows between 42° and 55°. The average high for August is 70° with an average low of 48°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how August weather will actually feel in Thunder Bay. See also: September | October | November.
