Clean your gutters too early and they refill within weeks; wait too long and you're on a ladder chipping ice off in freezing weather. Pros say the sweet spot is when roughly 70% of neighborhood leaves have fallen, timed to a window when temperatures are still 40 to 50 degrees, since colder debris gets far harder — and eventually impossible — to clear safely. Miss that window and the fix gets expensive fast, with frozen gutters risking fascia damage and ice dams that push water back under the roof.