according to this website: http://www.nodc.noaa.gov/dsdt/cwtg/all.html, about till thanksgiving. i have a feeling that trying to do the full winter in a 4/3 in RI wouldn't be so enjoyable, esp. if you go out on the colder, windier days.
i dunno, up there itll probably take you till december if the weather holds up the way it has been. if its colder, you'll either have to sack up or buy a 5/4 or whatever amount of rubber you think you need
yeah i surfed a few times in February in RI and wouldn't have been out there too long in a 4/3. I bet the 4/3 would get you to December though. I use a Hyperflex Flow hooded 6/5/4 with 7 mil oniell boots and 5 mil hyperflex lobster claw gloves. keeps me nice and toasty in NE winters.