weather in new castle, in
Hourly Forecast Detailed. 1  0am:The New Castle, DE forecast for Aug 29 is 66 degrees and Overcast. 2  3am:The New Castle, DE forecast for Aug 29 is 65 degrees and Overcast. 3  6am:The New Castle, DE forecast for Aug 29 is 65 degrees and Overcast. 4  9am:The New Castle, DE forecast for Aug 29 is 67 degrees and Light drizzle.