S
M
T
W
T
F
S
30
88°
65°
31
87°
66°
1
86°
65°
2
86°
62°
3
85°
61°
4
85°
61°
5
86°
62°
6
86°
61°
7
87°
62°
8
89°
65°
9
88°
62°
10
87°
61°
11
89°
63°
12
88°
64°
13
89°
65°
14
89°
63°
15
88°
63°
16
89°
64°
17
88°
63°
18
86°
62°
19
85°
61°
20
85°
60°
21
86°
61°
22
86°
61°
23
84°
61°
24
Hist. Avg.
82°
63°
25
Hist. Avg.
81°
63°
26
Hist. Avg.
81°
63°
27
Hist. Avg.
81°
62°
28
Hist. Avg.
80°
62°
29
Hist. Avg.
80°
62°
30
Hist. Avg.
80°
61°
1
Hist. Avg.
80°
61°
2
Hist. Avg.
79°
60°
3
Hist. Avg.
79°
60°
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 84° to 89°, with overnight lows between 60° and 66°. The average high for September is 87° with an average low of 63°. 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.
