Crossing the pond will be fairly cool, probably jst a few degrees above freezing. The sea will most probably be fairly rough of couse, January is the month for storms.
As you get into the Newfoundland coast and into New york you can expect the temperatures to drop to below freezing say -10C or 15F.
As you head south to Fort Lauderdale the temperatures will increase possibly as high as 20C+ or 70F+. You have a fair chance of rain in January around Florida.
As you head round to LA the temperatures will remain warm and will probably get drier.
A real mixed bag.
Jon