The morning temps here in New England have been in the low 40's, with the daytime highs only in the low 60's. We've already had our first frost. I suspect we'll see a hard freeze before too much longer!
So, yeah, I dress as if I were fishing in winter from this point on. Get yourself a set of "Under-All" long johns - Cabelas has their own brand at a very reasonable price. I also wear wool shirts, a wool hat and a set of Carhart insulated coveralls on top. I've fished in situations where we had to break ice to launch, so I know this stuff works. Included in my cold weather gears is a pair of rag wool, fingerless gloves. They are warm even when wet. Amazing. And of course, I keep a pair of those cheap, chemical hand warmers in each pocket of the coveralls as well.
Also, do a google search for Sorel boot pacs, with the felt liners. These are the boots with the rubber bottoms and leather uppers. Wear these with a pair of wool boot socks and your feet will not get cold. I've worn this particular pair for over 35 years. They're still going strong. And they work. I have no idea what a pair cost today though - or even if they still make them. But I'm sure someone does. A very popular boot style.
If you are worried about falling overboard, stay off the water - period. Nothing's going to help you in that situation. Always fish with a buddy and make sure you both have cell phones. Be safe!
"A voyage in search of knowledge need never abandon the spirit of adventure."