The right window is after most of the leaves have dropped but before the first hard freeze — in this area, typically mid-October through late November. Go too early and you'll be back out after the next windy afternoon. Wait too long and you're pulling frozen leaves out of frozen beds, which costs more and works worse. Properties with mature oaks usually need more than one visit, since oaks hold their leaves for weeks after everything else is bare. If you have gutters under heavy tree cover, they should be cleared in the same window. Packed gutters in November are what become ice dams in January.