S
M
T
W
T
F
S
30
78°
59°
31
78°
62°
1
79°
62°
2
80°
59°
3
79°
53°
4
77°
53°
5
75°
54°
6
76°
53°
7
80°
55°
8
82°
58°
9
83°
60°
10
82°
52°
11
76°
53°
12
76°
57°
13
77°
50°
14
74°
50°
15
72°
49°
16
73°
48°
17
74°
53°
18
75°
48°
19
76°
48°
20
74°
51°
21
78°
50°
22
74°
55°
23
78°
55°
24
76°
54°
25
74°
54°
26
78°
53°
27
78°
53°
28
79°
52°
29
79°
52°
30
77°
53°
1
78°
53°
2
78°
46°
3
77°
41°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Williamsport
Williamsport's September 2026 forecast shows daily high temperatures ranging from 72° to 83°, with overnight lows between 41° and 62°. The average high for September is 77° 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 Williamsport. See also: October | November | December.
