S
M
T
W
T
F
S
30
71°
50°
31
72°
58°
1
75°
59°
2
71°
60°
3
77°
60°
4
81°
57°
5
82°
55°
6
73°
49°
7
69°
49°
8
71°
56°
9
74°
51°
10
75°
55°
11
73°
50°
12
72°
56°
13
73°
55°
14
78°
53°
15
71°
54°
16
68°
53°
17
67°
54°
18
68°
48°
19
74°
46°
20
66°
52°
21
70°
44°
22
67°
45°
23
66°
43°
24
67°
44°
25
70°
49°
26
71°
45°
27
65°
52°
28
66°
47°
29
70°
41°
30
62°
49°
1
68°
45°
2
72°
44°
3
64°
42°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Idaho
Idaho's September 2026 forecast shows daily high temperatures ranging from 62° to 82°, with overnight lows between 41° and 60°. The average high for September is 71° with an average low of 51°. 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 Idaho. See also: October | November | December.
