S
M
T
W
T
F
S
30
77°
60°
31
76°
59°
1
76°
57°
2
73°
56°
3
73°
57°
4
76°
56°
5
76°
60°
6
72°
58°
7
72°
57°
8
74°
60°
9
74°
56°
10
71°
55°
11
78°
59°
12
78°
61°
13
75°
55°
14
71°
56°
15
73°
56°
16
73°
54°
17
70°
53°
18
70°
52°
19
71°
52°
20
69°
50°
21
69°
54°
22
70°
58°
23
69°
56°
24
71°
51°
25
68°
50°
26
67°
51°
27
67°
49°
28
68°
49°
29
67°
50°
30
66°
49°
1
66°
53°
2
68°
54°
3
67°
52°
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 66° to 78°, with overnight lows between 49° and 61°. The average high for September is 71° with an average low of 55°. 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.
