Como, as well as all the major lakes in the area, have "micro-climates" that are usually warmer than the surrounding environs.

Things vary according to the year, but I'd say that September/October is too early to see any autumnal foliage, especially now with global warming. In mid-late October you're likely to see fir trees and pines turn golden at (much) higher altitudes than the lakes. Late October/November is where you see more autumnal foliage but I have to say that NW Italy woods often lack the drama of places like New England. Below, for instance, is how my father's area (NW Italy, Piedmont, ranging from 500 to 2500 metres of altitude) looks like in early November.


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Temperatures in September will be in the low-mid 20s C, up to the low 20s in October if it's sunny.

As for being quiet: Como is a medium sized town in Milan's commuter belt and there's a lot of industry just south of it, so it won't be deserted. Also, if you're going there on a weekend there'll be plenty of day trippers from the city: it's not cold enough to go skiing yet and it's too late to head for the seaside.