S
M
T
W
T
F
S
30
80°
66°
31
90°
70°
1
91°
70°
2
86°
66°
3
80°
67°
4
78°
69°
5
78°
60°
6
82°
59°
7
81°
55°
8
71°
68°
9
82°
53°
10
78°
50°
11
79°
60°
12
76°
52°
13
71°
55°
14
66°
55°
15
68°
49°
16
69°
52°
17
68°
49°
18
65°
47°
19
66°
45°
20
65°
47°
21
70°
46°
22
69°
51°
23
71°
52°
24
73°
52°
25
73°
51°
26
70°
51°
27
71°
52°
28
73°
52°
29
71°
51°
30
71°
52°
1
68°
47°
2
62°
44°
3
59°
39°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Thornton
Thornton's September 2026 forecast shows daily high temperatures ranging from 59° to 82°, with overnight lows between 39° and 68°. The average high for September is 70° 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 Thornton. See also: October | November | December.
