S
M
T
W
T
F
S
30
84°
59°
31
83°
63°
1
83°
60°
2
82°
60°
3
83°
56°
4
83°
54°
5
81°
53°
6
72°
52°
7
72°
53°
8
73°
60°
9
70°
54°
10
72°
57°
11
73°
50°
12
71°
56°
13
71°
59°
14
72°
56°
15
70°
53°
16
68°
51°
17
70°
53°
18
72°
56°
19
78°
53°
20
78°
52°
21
77°
49°
22
68°
47°
23
67°
50°
24
68°
51°
25
66°
47°
26
66°
49°
27
67°
51°
28
67°
51°
29
65°
48°
30
64°
48°
1
65°
52°
2
68°
55°
3
72°
51°
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 84°, with overnight lows between 47° and 63°. The average high for September is 73° with an average low of 53°. 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.
