So Dave and I went out to the Maryland Chute. The air temperature was in the mid 50's and the water was in the upper 30s. This is the coldest water I've paddled in so far, and I never thought I would be paddling
and rolling in water this cold, but it wasn't too bad because it was sunny and the air was relatively warm. So for my personal tolerance, as long as I have my neoprene head warmer, a good drytop, and good fleece insulation underneath, I'm doing fine because I know I'm not going to exit the boat and I know how to control my gasp reflex.
Paddling while the snow is melting all around is beautiful. I wish I had my camera. One of the side streams was completely iced over, and at the MD Chute there was snow and ice all over the rocks that made for a great background while we were paddling.
So which parts of me got cold? My hands and my toes. The neoprene booties I was wearing did not provide enough insulation given that the only thing between them and the near-freezing water was a few millimeters of plastic. I wish I could wear my fleece socks under the booties but there isn't enough room, and if I get thicker booties they may not fit in the boat, so there I am paddling with cold toes. Maybe I'll start stuffing those chemical toe warmers in my booties before paddling.

As for my hands, I had pogies on the paddle so my hands were warm out of the water, but when I'm splashing around on the wave the water will get into the pogies. So after each ride I have to drain the pogies and wait a minute so my fingers can warm up before the next ride. I could probably wear some neoprene gloves under the pogies, but I like the feel of the paddle in my hands so I'm not sure how that would affect my paddling. Maybe that's something to try for later.