You're lucky: you live in New York (if you can call that "lucky"
). At least you have a break in the flea season.
Down here, it's 24/7/365: it never gets cold enough to kill off the existing population. Here where I live, it's been dry, so we haven't even been able to drown them out. The flea population is alive and well -- *thriving*, even.
"Monthly" meds are frequently overdosed to ensure adequate coverage during overlap periods. Stretch it out as long as you can: it saves you money and your pup the extra pesticide in its system. You can't fault it if it works.