S
M
T
W
T
F
S
30
91°
68°
31
88°
67°
1
86°
67°
2
87°
66°
3
87°
67°
4
89°
67°
5
89°
66°
6
90°
67°
7
89°
66°
8
88°
65°
9
89°
66°
10
90°
66°
11
90°
65°
12
89°
65°
13
88°
64°
14
89°
64°
15
89°
63°
16
88°
63°
17
87°
64°
18
87°
64°
19
88°
63°
20
87°
63°
21
85°
61°
22
84°
60°
23
81°
57°
24
85°
58°
25
81°
57°
26
82°
54°
27
85°
57°
28
87°
59°
29
87°
59°
30
86°
58°
1
86°
57°
2
85°
58°
3
85°
58°
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 81° to 91°, with overnight lows between 54° and 68°. The average high for September is 87° 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 Monticello. See also: October | November | December.
