S
M
T
W
T
F
S
30
80°
51°
31
80°
52°
1
79°
51°
2
80°
52°
3
74°
51°
4
72°
50°
5
73°
50°
6
75°
49°
7
75°
49°
8
77°
50°
9
71°
49°
10
71°
49°
11
73°
48°
12
74°
48°
13
73°
47°
14
71°
44°
15
67°
41°
16
68°
43°
17
73°
45°
18
76°
46°
19
74°
43°
20
73°
43°
21
71°
45°
22
74°
42°
23
70°
44°
24
75°
44°
25
74°
45°
26
75°
41°
27
75°
44°
28
74°
43°
29
71°
41°
30
70°
40°
1
72°
39°
2
66°
37°
3
65°
36°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Flagstaff
Flagstaff's September 2026 forecast shows daily high temperatures ranging from 65° to 80°, with overnight lows between 36° and 52°. The average high for September is 73° with an average low of 45°. 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 Flagstaff. See also: October | November | December.
