S
M
T
W
T
F
S
30
84°
56°
31
78°
67°
1
88°
70°
2
72°
67°
3
88°
68°
4
86°
73°
5
81°
65°
6
79°
61°
7
81°
55°
8
82°
61°
9
86°
69°
10
87°
64°
11
81°
54°
12
78°
58°
13
83°
60°
14
82°
60°
15
80°
59°
16
77°
55°
17
77°
56°
18
76°
56°
19
76°
53°
20
75°
52°
21
78°
56°
22
70°
56°
23
70°
56°
24
71°
55°
25
72°
54°
26
76°
52°
27
73°
49°
28
73°
53°
29
76°
54°
30
76°
54°
1
75°
53°
2
75°
54°
3
74°
51°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Princeton
Princeton's September 2026 forecast shows daily high temperatures ranging from 70° to 87°, with overnight lows between 49° and 69°. The average high for September is 77° with an average low of 56°. 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 Princeton. See also: October | November | December.
