S
M
T
W
T
F
S
30
70°
46°
31
73°
50°
1
69°
51°
2
69°
45°
3
70°
45°
4
73°
49°
5
69°
46°
6
68°
44°
7
69°
45°
8
72°
44°
9
76°
49°
10
77°
53°
11
77°
49°
12
76°
53°
13
77°
53°
14
73°
43°
15
72°
44°
16
72°
49°
17
76°
51°
18
77°
47°
19
76°
50°
20
75°
49°
21
68°
50°
22
74°
51°
23
75°
48°
24
73°
49°
25
73°
52°
26
74°
52°
27
74°
50°
28
64°
47°
29
62°
45°
30
63°
47°
1
62°
45°
2
60°
41°
3
59°
42°
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 59° to 77°, with overnight lows between 41° and 53°. The average high for September is 71° with an average low of 48°. 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.
