S
M
T
W
T
F
S
30
78°
52°
31
78°
48°
1
77°
52°
2
82°
51°
3
82°
52°
4
81°
47°
5
76°
51°
6
77°
50°
7
75°
49°
8
72°
47°
9
73°
45°
10
72°
45°
11
73°
44°
12
76°
44°
13
76°
45°
14
77°
52°
15
77°
49°
16
74°
43°
17
71°
41°
18
69°
40°
19
67°
41°
20
68°
41°
21
69°
44°
22
72°
49°
23
72°
49°
24
68°
48°
25
67°
49°
26
66°
39°
27
66°
39°
28
65°
44°
29
66°
43°
30
71°
46°
1
72°
46°
2
Hist. Avg.
71°
47°
3
Hist. Avg.
70°
46°
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 65° to 82°, with overnight lows between 39° and 52°. The average high for September is 73° with an average low of 46°. 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.
