From personal experience, I notice retardation increases in the winter season. Maybe the cold weather where I live fucks with people's heads, but it's noticeable.

One good example is through commuting to work. There's nary a snowflake on the ground, but god people seem to have their brains shut off, can't stay in their lanes, or they think they're driving in snow. Granted, there are retards on the road year round, but it feels like it increases in winter.