S
M
T
W
T
F
S
29
30°
19°
30
33°
20°
1
33°
18°
2
32°
15°
3
33°
15°
4
30°
14°
5
32°
15°
6
29°
13°
7
32°
8°
8
30°
4°
9
22°
9°
10
24°
5°
11
28°
5°
12
21°
11°
13
21°
12°
14
29°
12°
15
30°
6°
16
29°
4°
17
24°
-4°
18
20°
-4°
19
16°
8°
20
24°
9°
21
27°
11°
22
29°
7°
23
30°
5°
24
27°
6°
25
21°
7°
26
24°
9°
27
27°
5°
28
27°
4°
29
25°
7°
30
22°
-6°
31
25°
-14°
1
26°
-14°
2
6°
-7°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Thunder Bay
Thunder Bay's December 2026 forecast shows daily high temperatures ranging from 6° to 33°, with overnight lows between -14° and 20°. The average high for December is 26° with an average low of 7°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how December weather will actually feel in Thunder Bay. See also: January | February | March.
