S
M
T
W
T
F
S
30
80°
58°
31
75°
66°
1
88°
68°
2
83°
69°
3
85°
67°
4
83°
60°
5
80°
55°
6
77°
58°
7
79°
59°
8
76°
57°
9
75°
59°
10
78°
58°
11
76°
57°
12
74°
55°
13
76°
56°
14
74°
55°
15
75°
59°
16
74°
60°
17
75°
52°
18
70°
49°
19
70°
51°
20
74°
56°
21
78°
58°
22
78°
59°
23
79°
58°
24
78°
56°
25
77°
55°
26
76°
55°
27
77°
56°
28
76°
56°
29
75°
52°
30
69°
48°
1
67°
47°
2
70°
53°
3
74°
54°
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 67° to 88°, with overnight lows between 47° and 69°. The average high for September is 76° with an average low of 57°. 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.
