S
M
T
W
T
F
S
30
90°
62°
31
91°
61°
1
90°
57°
2
79°
60°
3
81°
60°
4
84°
56°
5
84°
54°
6
83°
57°
7
85°
60°
8
88°
62°
9
89°
62°
10
88°
57°
11
81°
59°
12
86°
58°
13
87°
59°
14
87°
57°
15
86°
56°
16
85°
49°
17
79°
48°
18
80°
54°
19
72°
45°
20
80°
55°
21
86°
57°
22
85°
52°
23
Hist. Avg.
77°
50°
24
Hist. Avg.
76°
50°
25
Hist. Avg.
76°
50°
26
Hist. Avg.
76°
49°
27
Hist. Avg.
75°
49°
28
Hist. Avg.
75°
49°
29
Hist. Avg.
74°
48°
30
Hist. Avg.
74°
48°
1
Hist. Avg.
73°
47°
2
Hist. Avg.
72°
47°
3
Hist. Avg.
72°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Boise
Boise's September 2026 forecast shows daily high temperatures ranging from 72° to 91°, with overnight lows between 45° and 62°. The average high for September is 84° with an average low of 57°. 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 Boise. See also: October | November | December.
