S
M
T
W
T
F
S
29
38°
16°
30
40°
20°
1
37°
19°
2
36°
19°
3
38°
18°
4
36°
18°
5
36°
17°
6
35°
13°
7
33°
14°
8
39°
17°
9
39°
16°
10
34°
16°
11
24°
3°
12
23°
6°
13
31°
8°
14
32°
6°
15
30°
8°
16
35°
7°
17
35°
14°
18
32°
12°
19
30°
11°
20
31°
11°
21
30°
7°
22
36°
3°
23
25°
0°
24
23°
3°
25
23°
7°
26
32°
13°
27
32°
13°
28
36°
14°
29
31°
12°
30
34°
11°
31
33°
1°
1
29°
0°
2
23°
6°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
December Weather in Johnstown
Johnstown's December 2026 forecast shows daily high temperatures ranging from 23° to 40°, with overnight lows between -0° and 20°. The average high for December is 32° with an average low of 11°. 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 Johnstown. See also: January | February | March.
