S
M
T
W
T
F
S
30
88°
68°
31
90°
70°
1
89°
70°
2
88°
63°
3
85°
62°
4
83°
61°
5
83°
63°
6
85°
66°
7
85°
66°
8
87°
68°
9
90°
68°
10
86°
62°
11
85°
61°
12
84°
67°
13
87°
60°
14
87°
59°
15
82°
58°
16
81°
59°
17
82°
58°
18
83°
59°
19
84°
59°
20
85°
61°
21
87°
64°
22
86°
63°
23
80°
63°
24
81°
62°
25
80°
60°
26
84°
60°
27
85°
59°
28
85°
60°
29
84°
60°
30
85°
59°
1
85°
60°
2
84°
58°
3
85°
52°
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 80° to 90°, with overnight lows between 52° and 70°. The average high for September is 85° with an average low of 62°. 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.
