Summer water temperatures in the shallow areas of Clear Lake were slightly higher and had a greater daily range than temperatures measured in the limnetic zone. The lake was not thermally stratified, although small differences sometimes were found between surface and bottom temperatures at the deepest point. Temperatures measured in the Clear Lake Water Treatment Plant were representative of those measured in the limnetic zone of the lake and provide a useful index of temperature conditions in the lake as a whole. The average annual temperature curve is asymmetrical, with the highest temperature falling on August 5 and the lowest occurring 119 days later on November 30. The median and mean lake temperatures were 51° and 53.7°F. The median date of ice breakup was April 3 and the median date of freezing was November 27
