S
M
T
W
T
F
S
30
76°
54°
31
72°
58°
1
79°
66°
2
66°
61°
3
81°
63°
4
79°
56°
5
75°
54°
6
73°
47°
7
75°
52°
8
75°
53°
9
74°
61°
10
75°
51°
11
69°
49°
12
72°
53°
13
71°
52°
14
75°
54°
15
76°
51°
16
73°
48°
17
69°
45°
18
65°
44°
19
71°
48°
20
72°
51°
21
72°
49°
22
71°
49°
23
68°
48°
24
68°
46°
25
67°
46°
26
70°
50°
27
69°
49°
28
63°
43°
29
60°
42°
30
61°
41°
1
59°
38°
2
59°
43°
3
58°
41°
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 58° to 81°, with overnight lows between 38° and 63°. The average high for September is 70° with an average low of 49°. 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.
