what si the average temp of Lake ontario
Answered by The Community. Making the world better, one answer at a time. The average temperature of Lake Ontario is 68 degrees Fahrenheit. The temperature is taken at the Monroe county water treatment plant every day.hat is the average temperature in the Great Lakes St Lawrence Lowlands? The average temperature in The Great Lakes and Lowlands of St.Lawrence are roughly around 20 to 30 degress celcius in the summer, and in the winter are around -15 to -25 degre â¦ es celcius.