A cold, perfect July 16 in Evanston

I invited Joe and Ken to swim at Evanston assuring them it would be a perfect day, water temperature included. When we got there the Lake was glass smooth. I realized my credibility was in trouble, smooth often means cold. It was a mere 61 F. But these guys are tough enough so once they stopped complaining and started to swim they agreed it was a perfect day: sunny, air in the mid 70's, no wind, clear water and, of course, no waves, and nothing else (boats or people) in the water.