I ride 12 months/year in Minnesota, so I'm not sure how one defines the end of the season. For sure, there's less light now than in August and that's causing changes - my weekday after-work club rides are gone and so I ride solo - usually after dark with good lights. Overall, this means that the miles/week are going down, but except for extreme weather (personal definition= below 10°F or unusually icy or stormy), it's always a good day to ride outside.