buxtons, here's a good temperature reading for Boston.
http://www.nodc.noaa.gov/dsdt/cwtg/natl.html
I forget, but someone posted a rule of thumb which added the air and water temps together to get a minimum for the kind of cold weather gear needed. Folks do sail in the dead of winter (I'm not one), but they are prepared for it like the dickens.
I've surfed here in CA on cold winter days, and being in direct contact with the water constantly I know it doesn't take long for unprotected hands to stop working, then try to unrig your boat. Yeah. . . we needed to help each other getting out of our wetsuits, and then just unlocking the car door I had to use the two edges of my hands below my pinkey finger to hold and turn the key. So although you might not die, if the temps are low enough you may lose hand functions and coordination which lead to other problems.
It sounds like your excursion might not be worth the effort you would need.