S
M
T
W
T
F
S
30
83°
61°
31
87°
62°
1
88°
63°
2
83°
60°
3
79°
58°
4
84°
60°
5
85°
61°
6
88°
62°
7
89°
62°
8
88°
61°
9
87°
61°
10
86°
60°
11
82°
57°
12
80°
58°
13
75°
50°
14
73°
47°
15
73°
48°
16
78°
55°
17
84°
59°
18
75°
54°
19
71°
47°
20
72°
50°
21
73°
46°
22
70°
46°
23
72°
48°
24
73°
47°
25
75°
45°
26
72°
46°
27
72°
42°
28
69°
38°
29
64°
39°
30
64°
42°
1
66°
43°
2
68°
45°
3
74°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Boise
Boise's September 2026 forecast shows daily high temperatures ranging from 64° to 89°, with overnight lows between 38° and 63°. The average high for September is 77° with an average low of 52°. 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.
