S
M
T
W
T
F
S
30
75°
54°
31
74°
61°
1
77°
54°
2
74°
55°
3
75°
52°
4
80°
58°
5
73°
51°
6
73°
51°
7
74°
50°
8
74°
52°
9
73°
55°
10
75°
53°
11
73°
54°
12
75°
53°
13
77°
52°
14
75°
54°
15
76°
59°
16
80°
59°
17
80°
58°
18
79°
54°
19
74°
50°
20
77°
53°
21
76°
50°
22
74°
50°
23
73°
57°
24
69°
56°
25
67°
50°
26
67°
53°
27
68°
50°
28
65°
51°
29
65°
56°
30
66°
58°
1
65°
57°
2
69°
47°
3
65°
46°
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 65° to 80°, with overnight lows between 46° and 61°. The average high for September is 73° with an average low of 54°. 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.
