S
M
T
W
T
F
S
30
76°
62°
31
71°
65°
1
84°
65°
2
75°
64°
3
76°
57°
4
75°
54°
5
74°
53°
6
74°
54°
7
75°
51°
8
76°
52°
9
75°
63°
10
73°
51°
11
72°
46°
12
78°
47°
13
73°
53°
14
64°
45°
15
69°
45°
16
69°
53°
17
70°
52°
18
65°
43°
19
64°
42°
20
68°
42°
21
N/A
22
63°
41°
23
66°
41°
24
66°
37°
25
68°
42°
26
71°
44°
27
70°
51°
28
69°
46°
29
69°
49°
30
67°
47°
1
65°
48°
2
66°
51°
3
59°
49°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Thornton
Thornton's September 2026 forecast shows daily high temperatures ranging from 59° to 71°, with overnight lows between 37° and 51°. The average high for September is 67° with an average low of 46°. 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 Thornton. See also: October | November | December.
