S
M
T
W
T
F
S
30
70°
59°
31
76°
62°
1
73°
62°
2
74°
58°
3
69°
56°
4
69°
56°
5
70°
58°
6
72°
60°
7
76°
59°
8
72°
55°
9
66°
53°
10
68°
57°
11
65°
45°
12
63°
51°
13
62°
50°
14
64°
49°
15
63°
47°
16
64°
48°
17
64°
47°
18
63°
47°
19
62°
44°
20
60°
43°
21
61°
44°
22
63°
52°
23
67°
49°
24
71°
54°
25
72°
54°
26
73°
53°
27
71°
48°
28
70°
52°
29
62°
45°
30
59°
49°
1
59°
53°
2
68°
42°
3
70°
40°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Thornhill
Thornhill's September 2026 forecast shows daily high temperatures ranging from 59° to 76°, with overnight lows between 40° and 62°. The average high for September is 67° 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 Thornhill. See also: October | November | December.
