S
M
T
W
T
F
S
30
89°
69°
31
90°
70°
1
93°
66°
2
89°
67°
3
94°
72°
4
91°
70°
5
73°
70°
6
90°
68°
7
88°
62°
8
88°
68°
9
91°
70°
10
90°
67°
11
81°
66°
12
86°
62°
13
89°
65°
14
89°
67°
15
86°
66°
16
83°
61°
17
81°
57°
18
76°
54°
19
76°
54°
20
73°
52°
21
76°
55°
22
79°
60°
23
82°
60°
24
83°
61°
25
83°
61°
26
82°
60°
27
83°
60°
28
83°
59°
29
82°
60°
30
82°
59°
1
81°
58°
2
77°
50°
3
69°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Monticello
Monticello's September 2026 forecast shows daily high temperatures ranging from 69° to 91°, with overnight lows between 47° and 70°. The average high for September is 82° with an average low of 60°. 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 Monticello. See also: October | November | December.
