Fall is flea season,  even though you may notice that ticks seem to be less of a problem warm fall weather is great for fleas.  It is particularly bad if you go into the cooler months with fleas already in your house, the fleas multiply in the warm areas of your house.  The bottom line is to keep putting flea and tick protection on your dogs and cats through out the fall until it gets really cold for a few weeks. Here in Long Island that is usually not until December.