Hi Mickey,
It doesn't have to be extremely cold for a drysuit to be worthwhile. I guess it's more about the water temperature than it is the air temp.
Glenn_Southriver & I were out on the Chesapeake Bay this past weekend (27-30kt sustained & 35-40kt gusts on Saturday - WHAT A RIDE!
). While the air temps were mild, low 50's to upper 60's Fahrenheit. the water temp was only 47 degrees. I was dressed in jeans & long-johns, and thermal shirt, t-shirt & sweatshirt, with heavy socks. Glenn usually goes with sweatpants rather than jeans. Either works fine. I was quite comfortable. I never felt cold, and the only time I felt "warm" was when the wind died for a spell on Sunday, and we were peddling in the bright sun. Dark color suit & warm sun... we were warm, but not hot. Fixed this by dragging our feet & legs in the water for a few minutes. It's an kind of an odd feeling to feel like you're wet, but are actually still dry.
We were out one nice day last spring when the air was about 72 degrees, but the water was still below 45. That time I went without the sweatshirt. Was comfortable the whole time. I did jump into the 40 something water that day, just to see if it really did keep me completely dry. I could feel that it was cooler, but even after about 15 minutes in the water, I wasn't what I consider cold. Suit was quite buoyant, too. When we did our New Years Day Polar Bear Sail, I added a flannel shirt layer and a pair of neoprene socks. Again, I was quite comfortable. I decided not to try jumping in that day. If you do get a little warm, I've found that this usually results in the air inside the suit expanding a bit (feel like the Michelin Tire Man). Just pull the neck gasket out a bit to "burp" the suit, and that seems to let a little cool air in at the same time.
One thing about the sewn on socks/booties though. Don't walk in just those. The material is not very thick. It's designed for waterproofing, not for walking. When you pull on the suit, immediately follow with a pair of water shoes, boots, or similar item. Don't want to tear that material on a rock, dock nail, splinter, etc.
If you're looking to extend your season, I'd say a drysuit is a worthwhile investment. The only thing that kept Glenn & I off the water during the rest of January & February this year was our schedules. There were a number of days that we would've been out there if other obligations hadn't gotten in the way.
Happy Sailing,
- Jim L