I got an email asking about lake temps. Here's the latest satellite data for the great lakes. (above) And below is another, higher resolution image for the north half of Lake Michigan.
The black areas indicate cloud cover and no surface temp data.
Surface water temps are lower on the western side of Lake Michigan due to the prevailing west winds that push the wamer surface water to the east and cause the deeper, colder water to upwell just offshore. (in the top color image, you can see the green line of cold water along the shorline of Wisconsin on the west side of Lake Michigan)
This can happen even in the middle of summer and many a sailor has been surprised to launch in a shorty with air temps in the 80's and shoreline water temps in the upper 60's/low 70's only to find that a few hundred yards offshore, they are in 34 degree water and could get into a serious hypothermia situation.
This time of year demands a drysuit, booties, hood and mitts. When the conditions are really nasty, I prefer my GoreTex "super suit" with integrated footies where only my head and hands are exposed.
Its soooo comfy - almost like being in the womb again. ;-)