This sunday, CSC (thats Carolina Sailing Club) is holding their winter series out at the local watering hole. I'm dying to sail. The air temp is 49 degrees, not sure about the water temp. Most of the boats are mono's although my friend Robert has sailed his 18SX out there during the middle of january before. There are two motor boats, a committee and a chase/rescue boat on the course. I've got a full wetsuit but not a dry suit. I have plenty of waterproof clothing to put over the wetsuit though, just not sealed.
Would you race or not? 
Heck yeah, I'd sail. We went to Alaska last year and sailed. See attachment.
Tracie
Okay, that was a joke. I just happened to have that picture because I used it in our Christams card.
To answer your question, I would not go sailing. Not even in my drysuit. I can't concentrate when I am that cold and its just no fun.
Tracie
see its not so much the cold air that get to me, its the potential third time to get hypothermia for me. The first two sucked... I didn't have a rescue boat the one time I was sailing though.
I would sail. We sail Hobie 14's in Newport, RI until it gets to about 20-30 degrees F. before windchill. It is cold but well worth the fun. 2 weeks ago I had a Hobie 16 out with just a wetsuit and spray gear on, it was about 50 degrees but there was only about 8 knots of wind and it wasn't too bad out. I stayed out like 4 hours.
I'm sure the answers to a question like this will quickly identify the geographic distribution of the respondants.
49 degrees? Well, that's still a bit too warm for any good ice. 
The water's still liquid on the broad lake, but the shallow bays have started to freeze. (Plus, we have had four feet of snow in the past couple weeks). Last time I was out sailing was around Thanksgiving, racing with the local J24 fleet. The air temp was right around freezing. Snow-capped peaks framed the background. Not a cloud in the sky. NW winds at 12-14 knots. It just doesn't get any better!
Ok, after living in "the south" for the better part of 10 years now, I don't exactly have anti-freeze running through my veins. At any rate, the decision has been made for me. My car started misfiring on the way to the pub tonight, so I picked up some spark plugs on the way back. Alas, I have a project to complete tomorrow.
I'll be sailing today, air temps around 70F, winds 15-25, and the water temp in the high 50's.
Here in the south, it's the 'poor man's drysuit'. Thermals, or wetsuit shorty, under a one piece spraysuit, with velcro cuffs.
The homebrew beer doesn't really help any, but I can't resist sometimes 
N6.0na
sq top, and apin
#111
Remember Tradewinds last year...I am born, raised and still live in South Florida. I remember standing on the Dock at Rowells Marina on Friday evening, 20 knots of 40 degree wind hitting me on the nose (and the fin) then making a mad dash for West Marine to get some foulies for me and crew. 12 hours and $400 later we were heading for the starting line and fairly warm. What a great day of sailing!
Lips and nose took a beating, but everything else was fine. So, if you have the equipment and the desire, SAIL ON ! YEE FREAKIN' HAAAAAWWWWWW!
we're still sailing here in beaufort, sc, we have a 'holiday series' of 5 race sundays, today is a race day! yeah! forecast calls for light and variable, sunny and low 50's. i'll be wearing a wet suit and insulated windbreaker.
As long as it is above 0 degrees Celcius, go ahead! We sail trough the whole winter here as long as it stays above 0 degrees. If it is below, the sheets freeze and the deck is covered in ice.
We use drysuits now, but have used wetsuits earlier. I would not reccomend using a wetsuit tough. If you decide to use a wet suit, put on some polyproylene or wool under it. Put on wool socks inside plastic bags before you stick your feet into any neoprene boots.
Some surfers neoprene gloves with open palms keeps your hands warm, put on a warm hat and you are clear to go.
Good luck!
I still shiver at the memory of Tradewinds last year...and I had a dry suit on (not a whole lot on underneath however). The odds are with us to have it be warm this year however!
Went with the full spraysuit and lots of "Frosty Fleece" underneath (built and sold here in FL). Was warm, but didn't stay out long on the water ("minor" incident with other boat).
For me, the cold certainly takes a bit of fun out of the sailing, because I have to spend more time piling on more layers, and I'm less likely to sail to the edge of performance, because flipping with be very cold and I won't be able to swim as well with all that crap on.
Still, I'd venture out on a cold, sunny day as long as the wind wasn't howling...
And just what was the windchill with 40 degrees and 30 kts?
That said - how does fleece perform IN the water? I know a wetsuit is really designed to keep you warm when you are submerged. I also know that fleece performs well out of the water if you keep the wind off it. What's that like in cold water with fleece on?
well I know it dries out almost instantly 😛
Depends on how LONG you're in the water... Fleece and wetsuit are both cold in the drink. Wetsuit warms faster, but when you get out you get the refrigerator effect in the breeze, which makes the wetsuit feel COLDER in the wind. The fleece dries faster, and still maintains some warmth when wet (but not as much as the wetsuit). Wind does cut right through the fleece, so you need some wind protection over it...
The wetsuit does, however, provide less drag when swimming after a sideways cat drifting away at 4 knots!
I prefer the fleece over the wetsuit for range of motion while sailing, as well as it's ability to breathe. It's also easier to don/doff than a wetsuit. If you put wicking undergarments on (rasher), you don't get as clammy underneath as you would with a wetsuit when you get hot.
I think if it got REALLY cold, I'd switch to a drysuit from the fleece/spray combo, and leave out the wetsuit unless I planned on being in the drink a LOT (like surfsailing)
With my current spraysuit/fleece combo, it actually takes a bit of work to get the fleece completely wet, as the harness and spray gear keep the trunk area from too much water intrusion. Last time I dropped in the drink, the full harness and spray gear setup kept my midsection dry for the two minutes it took me to get the boat back up. The legs and arms were soaked, but the spray gear kept the wind off them until they dried a little while later.
my getup would be:
Full 3-4mm wetsuit
full fleece jacket top
Dryshirt
Foulies
then some of them wetsuit booties and those hefty west marine gloves.
Something for the head... prolly just a cap that comes down over the ears, and some shades 😛
Burrrrrrrr,
...here is an invite...
..come down to St. Croix for the International Regatta the 2nd weekend in Feb ( about 6 weeks away)
..or come in the middle of MArch to Rolex- St.Thomas and BVI-Spring regatta -Tortola ( the following weekend)....you can get in 6 days of racing in 9 calander days!!....usually a container comes down that you can get your boat on,.....
...we would look forward to race with you all!
..oh yes,....water about 79 f,...air about 83,....bring sunblock, sandel and swimsuit to sail in.
regards,
Bruce
I-17
St. Croix 
its 85 here today going out nanny nanny....