I don't think they do.
They have a flag warning system on the beach. Red. NO swimming. Yellow swimming with warnings . Green swimming allowed . It it posted on the beach with a sign on the flagpole
When conditions are dangerous or the water is bad quality etc.
I think you're asking when is the season over? In that case, you stop when you stop. I'm pretty sure they leave that one up to the people. Figuring people will stop when the temperature of the lake drops. The flag system is for every day condtions and safety.
Swimming safety is posted in color signs. Green, yellow and red. Green means good, yellow means caution, red means no-go.
They have a flag warning system. You can easily see the flag color on the beach.
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