S
M
T
W
T
F
S
30
80°
60°
31
81°
60°
1
83°
62°
2
86°
65°
3
84°
65°
4
85°
61°
5
82°
59°
6
79°
58°
7
80°
60°
8
82°
63°
9
78°
62°
10
79°
63°
11
83°
62°
12
84°
63°
13
84°
62°
14
83°
63°
15
84°
62°
16
83°
62°
17
82°
61°
18
82°
57°
19
81°
58°
20
79°
52°
21
76°
55°
22
75°
58°
23
78°
57°
24
80°
52°
25
79°
52°
26
78°
56°
27
79°
57°
28
76°
55°
29
77°
54°
30
77°
55°
1
78°
53°
2
78°
54°
3
72°
55°
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 72° to 86°, with overnight lows between 52° and 65°. The average high for September is 80° with an average low of 59°. 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.
