S
M
T
W
T
F
S
30
79°
53°
31
80°
60°
1
84°
61°
2
78°
62°
3
86°
62°
4
87°
58°
5
85°
57°
6
81°
51°
7
77°
53°
8
83°
58°
9
84°
56°
10
84°
57°
11
80°
51°
12
79°
57°
13
81°
57°
14
84°
50°
15
75°
55°
16
74°
54°
17
73°
55°
18
74°
52°
19
79°
46°
20
73°
53°
21
77°
47°
22
76°
50°
23
77°
47°
24
79°
48°
25
79°
54°
26
78°
53°
27
77°
55°
28
78°
52°
29
78°
44°
30
70°
49°
1
76°
53°
2
77°
49°
3
75°
45°
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 87°, with overnight lows between 44° and 62°. The average high for September is 79° with an average low of 53°. 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.
