S
M
T
W
T
F
S
30
87°
56°
31
79°
60°
1
79°
63°
2
82°
55°
3
84°
61°
4
84°
63°
5
86°
59°
6
86°
54°
7
76°
54°
8
77°
53°
9
77°
56°
10
82°
59°
11
82°
53°
12
75°
53°
13
76°
52°
14
75°
59°
15
81°
56°
16
82°
50°
17
75°
50°
18
73°
49°
19
72°
50°
20
73°
51°
21
71°
51°
22
71°
49°
23
72°
51°
24
72°
53°
25
77°
55°
26
77°
55°
27
78°
47°
28
75°
53°
29
72°
54°
30
76°
53°
1
69°
51°
2
71°
47°
3
68°
44°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in New Castle
New Castle's September 2026 forecast shows daily high temperatures ranging from 68° to 87°, with overnight lows between 44° and 63°. The average high for September is 77° with an average low of 54°. 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. See also: October | November | December.
