I'll chart a few morning air and water temp readings here in Chicago for future reference. The National Championship 5k swim is September 12 in 2009 at Big Shoulders venue in Chicago.
Sept. 10, 2008:
6 a.m.
Water: 64 deg. F
Air: 52 deg. F
Sept. 14, 2008:
7:30 a.m.
Water: 67-69 deg. F
Air: 71 deg. F
Raining
Sept. 16, 2008:
6 a.m.
Water: mid- to upper 60s
Air: 51 deg. F
Sept. 17, 2008:
6 a.m.
Water: 65 deg F
Air: 58 deg. F
That's enough data to suggest that anyone swimming Big Shoulders on September 12, 2009, should plan for water temps in 60s and air temps quite conceivably in 50s.
