Kevin,

You are absolutely right, the temperature last week was 39 degrees out in the reefs. The temp that coastwatch is referring to is the average across the whole lake. Below is a link from noaa that shows the different temperatures in the different areas of the lake. If you notice the area around the reefs, it's in the
40's. With the weather forecast predicting warmer weather, we should be in the 42 degree range by Saturday.

http://www.glerl.noaa.gov/res/glcfs/...t&type=N&hr=00