S
M
T
W
T
F
S
30
75°
65°
31
84°
63°
1
80°
58°
2
79°
51°
3
81°
60°
4
81°
58°
5
85°
61°
6
84°
63°
7
79°
64°
8
82°
61°
9
72°
54°
10
83°
51°
11
76°
56°
12
62°
45°
13
63°
42°
14
59°
43°
15
67°
50°
16
68°
42°
17
69°
49°
18
70°
51°
19
73°
51°
20
59°
48°
21
65°
44°
22
67°
47°
23
67°
56°
24
65°
54°
25
70°
60°
26
67°
50°
27
67°
52°
28
64°
51°
29
63°
44°
30
65°
48°
1
65°
49°
2
62°
40°
3
63°
47°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Thief River Falls
Thief River Falls's September 2026 forecast shows daily high temperatures ranging from 62° to 70°, with overnight lows between 40° and 60°. The average high for September is 65° with an average low of 50°. 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 Thief River Falls. See also: October | November | December.
