S
M
T
W
T
F
S
30
90°
71°
31
93°
72°
1
97°
71°
2
99°
73°
3
97°
73°
4
97°
73°
5
99°
73°
6
99°
72°
7
86°
72°
8
91°
68°
9
91°
68°
10
95°
70°
11
95°
73°
12
84°
73°
13
93°
72°
14
95°
68°
15
91°
73°
16
90°
72°
17
91°
64°
18
97°
68°
19
91°
72°
20
90°
70°
21
91°
68°
22
88°
72°
23
79°
66°
24
70°
63°
25
77°
59°
26
82°
54°
27
84°
50°
28
82°
50°
29
86°
54°
30
90°
61°
1
88°
68°
2
89°
71°
3
83°
71°
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 83° to 89°, with overnight lows between 71° and 71°. The average high for September is 86° with an average low of 71°. 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.
