S
M
T
W
T
F
S
30
73°
53°
31
75°
59°
1
78°
61°
2
83°
60°
3
85°
60°
4
79°
53°
5
72°
53°
6
74°
58°
7
74°
53°
8
73°
53°
9
72°
57°
10
70°
58°
11
71°
57°
12
71°
54°
13
72°
57°
14
72°
58°
15
79°
59°
16
80°
51°
17
75°
51°
18
74°
50°
19
78°
53°
20
78°
59°
21
77°
54°
22
70°
51°
23
69°
53°
24
68°
49°
25
67°
50°
26
70°
49°
27
68°
57°
28
67°
56°
29
66°
52°
30
67°
54°
1
73°
56°
2
71°
55°
3
71°
50°
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 66° to 85°, with overnight lows between 49° and 61°. The average high for September is 73° with an average low of 55°. 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.
