I' sail through the whole year but only when the temp is above 0° C. I wear a breathable drysuit with 3 pair of socks and allot of clothes.
The chill factor when sailing is far greater, than it is when skiing (only when wet!). Skiing is also more athletic and you were nice skiing boots and gloves. The problem when sailing in low temp, is that your feeds and hands get wet and stiff after while.