S
M
T
W
T
F
S
30
84°
50°
31
82°
48°
1
81°
49°
2
87°
50°
3
88°
52°
4
87°
45°
5
78°
40°
6
76°
42°
7
78°
42°
8
76°
44°
9
77°
49°
10
84°
41°
11
82°
44°
12
78°
41°
13
78°
49°
14
83°
38°
15
80°
37°
16
72°
35°
17
70°
35°
18
69°
38°
19
71°
39°
20
72°
40°
21
78°
40°
22
74°
37°
23
70°
37°
24
67°
36°
25
67°
36°
26
66°
37°
27
67°
36°
28
66°
35°
29
66°
35°
30
69°
36°
1
Hist. Avg.
65°
37°
2
Hist. Avg.
64°
37°
3
Hist. Avg.
64°
37°
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 66° to 88°, with overnight lows between 35° and 52°. The average high for September is 76° with an average low of 41°. 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.
