S
M
T
W
T
F
S
30
81°
60°
31
82°
62°
1
83°
58°
2
73°
53°
3
76°
59°
4
77°
56°
5
Hist. Avg.
74°
39°
6
Hist. Avg.
74°
39°
7
Hist. Avg.
73°
38°
8
Hist. Avg.
73°
38°
9
Hist. Avg.
73°
38°
10
Hist. Avg.
72°
38°
11
Hist. Avg.
72°
37°
12
Hist. Avg.
72°
37°
13
Hist. Avg.
71°
36°
14
Hist. Avg.
71°
36°
15
Hist. Avg.
70°
36°
16
Hist. Avg.
70°
36°
17
Hist. Avg.
70°
35°
18
Hist. Avg.
69°
35°
19
Hist. Avg.
69°
34°
20
Hist. Avg.
69°
34°
21
Hist. Avg.
68°
34°
22
Hist. Avg.
68°
34°
23
Hist. Avg.
67°
33°
24
Hist. Avg.
67°
33°
25
Hist. Avg.
67°
32°
26
Hist. Avg.
66°
32°
27
Hist. Avg.
66°
32°
28
Hist. Avg.
65°
31°
29
Hist. Avg.
65°
31°
30
Hist. Avg.
64°
31°
1
Hist. Avg.
64°
30°
2
Hist. Avg.
64°
30°
3
Hist. Avg.
63°
30°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Boulder
Boulder's September 2026 forecast shows daily high temperatures ranging from 73° to 83°, with overnight lows between 53° and 62°. The average high for September is 79° with an average low of 58°. 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 Boulder. See also: October | November | December.
