S
M
T
W
T
F
S
29
47°
16°
30
40°
11°
1
37°
10°
2
40°
18°
3
45°
19°
4
39°
13°
5
38°
11°
6
37°
8°
7
35°
7°
8
37°
10°
9
45°
12°
10
45°
10°
11
44°
15°
12
46°
18°
13
47°
18°
14
40°
15°
15
40°
20°
16
42°
12°
17
39°
9°
18
38°
8°
19
39°
9°
20
38°
10°
21
40°
11°
22
39°
10°
23
39°
12°
24
40°
10°
25
39°
20°
26
41°
19°
27
46°
9°
28
40°
8°
29
38°
11°
30
40°
7°
31
38°
9°
1
39°
16°
2
43°
17°
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 35° to 47°, with overnight lows between 7° and 20°. The average high for December is 41° with an average low of 13°. 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.
