S
M
T
W
T
F
S
30
75°
58°
31
86°
65°
1
89°
71°
2
92°
70°
3
87°
68°
4
79°
66°
5
80°
57°
6
79°
54°
7
80°
53°
8
85°
53°
9
87°
65°
10
82°
59°
11
80°
61°
12
77°
66°
13
83°
58°
14
75°
60°
15
90°
65°
16
85°
66°
17
83°
62°
18
76°
54°
19
71°
50°
20
76°
55°
21
70°
53°
22
73°
53°
23
72°
50°
24
79°
54°
25
71°
50°
26
77°
54°
27
79°
54°
28
78°
52°
29
72°
50°
30
76°
54°
1
74°
50°
2
70°
50°
3
74°
52°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in New Castle Northwest
New Castle Northwest's September 2026 forecast shows daily high temperatures ranging from 70° to 90°, with overnight lows between 50° and 66°. The average high for September is 77° with an average low of 56°. 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 New Castle Northwest. See also: October | November | December.
