S
M
T
W
T
F
S
30
77°
50°
31
88°
55°
1
86°
64°
2
78°
60°
3
77°
46°
4
58°
46°
5
76°
48°
6
76°
53°
7
69°
47°
8
76°
49°
9
83°
51°
10
88°
55°
11
81°
56°
12
90°
58°
13
74°
54°
14
69°
49°
15
77°
49°
16
81°
49°
17
85°
60°
18
73°
57°
19
76°
53°
20
80°
56°
21
85°
57°
22
85°
58°
23
87°
56°
24
94°
59°
25
82°
55°
26
70°
43°
27
67°
51°
28
75°
49°
29
76°
51°
30
80°
51°
1
80°
53°
2
83°
52°
3
86°
56°
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 76° to 86°, with overnight lows between 51° and 56°. The average high for September is 81° 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.
