You probably know this already but I would advise avoiding the flea treatments that you can get in the supermarket, they do not work well and they can be very toxic to cats. Also, fleas can survive all year round in warm moist environments. Using a good quality flea product like Advantage or Frontline, etc. will keep the fleas out of your house all year long. When you use the bomb, prop up couch cushions, matresses, etc. A cat that has a load of fleas will drop hundreds of eggs every time it sits in one place for a few minutes so everywhere the cat goes will be a lot of eggs and these fall into cracks and crevices that can be protected from the bombing chemicals so eliminate any cracks and crevices if you can.
Also, the flea is the intermediate host for the dipylidium tapeworm (flea larvae eat tapeworm eggs and your cat eats the fleas when it grooms, thus ingesting the tapeworm) so you will need to deworm as well.
Good luck!