I just googled the snot outta water temp/Lake of the Woods. Some were claiming 60* in June. I can't believe it would actually get that warm. I wouldn't think it would be as bad as Superior with some rediculous annual average of 37*
If its warm enough for these little girls, it is warm enough for a catamaran sailor. They might be Canadian though...
The race is in early August giving it two more months to warm up after June. While the lake is large, it is not very deep. So, it warms quickly.
Here is what I was describing with the house boats as a moving base: