S
M
T
W
T
F
S
29
35°
27°
30
34°
25°
1
34°
26°
2
35°
31°
3
36°
32°
4
39°
32°
5
39°
35°
6
40°
34°
7
38°
34°
8
36°
32°
9
35°
30°
10
32°
31°
11
42°
28°
12
39°
29°
13
37°
25°
14
36°
20°
15
34°
22°
16
29°
23°
17
30°
26°
18
34°
29°
19
35°
31°
20
39°
32°
21
40°
31°
22
41°
31°
23
40°
33°
24
43°
27°
25
42°
23°
26
39°
20°
27
28°
19°
28
29°
29°
29
37°
28°
30
39°
31°
31
40°
32°
1
41°
29°
2
42°
23°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Sarnia
Sarnia's December 2026 forecast shows daily high temperatures ranging from 28° to 43°, with overnight lows between 19° and 35°. The average high for December is 37° with an average low of 28°. 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 Sarnia. See also: January | February | March.
