S
M
T
W
T
F
S
30
93°
68°
31
95°
70°
1
97°
70°
2
97°
70°
3
99°
72°
4
99°
73°
5
99°
72°
6
97°
72°
7
91°
68°
8
91°
73°
9
93°
73°
10
93°
74°
11
95°
70°
12
93°
68°
13
95°
66°
14
97°
70°
15
98°
73°
16
96°
71°
17
95°
70°
18
97°
68°
19
94°
72°
20
94°
71°
21
87°
68°
22
81°
60°
23
80°
57°
24
79°
57°
25
80°
58°
26
81°
59°
27
83°
58°
28
79°
53°
29
82°
58°
30
83°
59°
1
83°
59°
2
82°
58°
3
82°
59°
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 79° to 98°, with overnight lows between 53° and 73°. The average high for September is 86° with an average low of 63°. 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.
