-- Last Updated: Jan-27-13 12:34 PM EST --
Your best bet is probably the buoy data collection
for temps, wave heights, etc.
Bouys in Lake Superior recorded water temperatures
typically reach the mid-50s by early July
get up to 60s around late August.
As you head south in Michigan- add a few degrees.
It takes longer than people think before they are warm.
Dress for the water temps, not the air temps.
A buoy in the open waters of Lake Michigan
recorded 80 degree F temperatures in July 2012
- that has happened only six times since 1981.
Lake Huron in July is between 60-70 most years.
People often Over-Estimate the water temps.