Average approximate surface water temperature:
June 1: 65°
July 1: 74°
August 1: 82°
*Temperatures are taken at two feet below the surface at Water Safety Patrol H.Q.(between Williams Bay and Fontana) and averaged over the years beginning with 1991. Surface temperatures often fluctuate by 1° to 6° depending on the location of the lake (temperatures are generally a bit cooler on the west end of the lake near Fontana).
Waves: Since Lake Geneva is a long lake stretching from east to west, waves are at their greatest heights and force when there is a strong wind blowing from the east or west. Geneva Lake is calm on some days, while on some rare days there are waves as high as 5 feet or more. Of course the size of the waves is also influenced by “boat chop” created by boat wakes.