S
M
T
W
T
F
S
30
80°
56°
31
83°
60°
1
83°
61°
2
81°
60°
3
82°
52°
4
76°
51°
5
75°
52°
6
78°
59°
7
81°
59°
8
81°
58°
9
75°
56°
10
76°
58°
11
80°
57°
12
81°
58°
13
80°
58°
14
80°
57°
15
80°
57°
16
79°
56°
17
77°
51°
18
78°
48°
19
70°
46°
20
71°
46°
21
69°
45°
22
69°
49°
23
70°
46°
24
73°
45°
25
69°
52°
26
74°
53°
27
69°
52°
28
75°
52°
29
74°
51°
30
75°
50°
1
70°
49°
2
73°
51°
3
67°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Johnstown
Johnstown's September 2026 forecast shows daily high temperatures ranging from 67° to 83°, with overnight lows between 45° and 61°. The average high for September is 76° with an average low of 53°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Johnstown. See also: October | November | December.
