S
M
T
W
T
F
S
30
85°
51°
31
82°
49°
1
79°
50°
2
80°
51°
3
83°
56°
4
84°
52°
5
85°
51°
6
79°
49°
7
82°
46°
8
Hist. Avg.
82°
51°
9
Hist. Avg.
82°
50°
10
Hist. Avg.
81°
50°
11
Hist. Avg.
81°
50°
12
Hist. Avg.
80°
50°
13
Hist. Avg.
80°
49°
14
Hist. Avg.
80°
49°
15
Hist. Avg.
79°
48°
16
Hist. Avg.
79°
48°
17
Hist. Avg.
79°
48°
18
Hist. Avg.
78°
48°
19
Hist. Avg.
78°
47°
20
Hist. Avg.
77°
47°
21
Hist. Avg.
77°
46°
22
Hist. Avg.
76°
46°
23
Hist. Avg.
76°
46°
24
Hist. Avg.
76°
45°
25
Hist. Avg.
75°
45°
26
Hist. Avg.
74°
44°
27
Hist. Avg.
74°
44°
28
Hist. Avg.
74°
44°
29
Hist. Avg.
73°
43°
30
Hist. Avg.
73°
43°
1
Hist. Avg.
72°
42°
2
Hist. Avg.
72°
42°
3
Hist. Avg.
71°
42°
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 79° to 85°, with overnight lows between 46° and 56°. The average high for September is 82° with an average low of 51°. 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.
