S
M
T
W
T
F
S
30
75°
50°
31
83°
49°
1
88°
57°
2
86°
54°
3
86°
53°
4
87°
52°
5
78°
49°
6
78°
51°
7
79°
48°
8
79°
46°
9
75°
48°
10
80°
49°
11
79°
45°
12
72°
46°
13
79°
48°
14
82°
50°
15
82°
50°
16
84°
49°
17
80°
45°
18
71°
43°
19
78°
46°
20
81°
48°
21
76°
46°
22
75°
47°
23
81°
48°
24
81°
48°
25
69°
46°
26
76°
46°
27
78°
47°
28
78°
47°
29
76°
46°
30
76°
46°
1
75°
45°
2
74°
46°
3
72°
45°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Roundup
Roundup's September 2026 forecast shows daily high temperatures ranging from 69° to 88°, with overnight lows between 43° and 57°. The average high for September is 79° 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 Roundup. See also: October | November | December.
