S
M
T
W
T
F
S
30
88°
73°
31
90°
72°
1
90°
75°
2
93°
72°
3
91°
72°
4
90°
73°
5
91°
73°
6
91°
72°
7
90°
70°
8
90°
72°
9
91°
72°
10
90°
73°
11
86°
73°
12
86°
72°
13
91°
72°
14
95°
73°
15
93°
72°
16
88°
72°
17
88°
68°
18
91°
64°
19
93°
70°
20
88°
70°
21
88°
71°
22
88°
71°
23
88°
70°
24
87°
67°
25
86°
63°
26
85°
64°
27
83°
60°
28
85°
61°
29
83°
64°
30
84°
67°
1
82°
65°
2
83°
62°
3
86°
67°
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 82° to 93°, with overnight lows between 60° and 71°. The average high for September is 86° with an average low of 66°. 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.
