Slightly different issue, but still on feeding and time of year.

I am 85 miles South of St. Louis, and have noticed that since the nights have gotten cooler, the water temp is dropping, my feeding is received with less vigor than 2-3 weks ago. I don't necessarily want my feeding to become an issue on the pond bottom if not eaten.

What are the 'general' conditions/time of year when feeding become less effective an should be stopped?