Due to multiple factors, expect to potentially pay more when booking in December. For low rates, September can be a great choice for travel to Saint Petersburg. Flights to Saint Petersburg from Melbourne, Florida in September are about $1,084 on average during September, but can be found for as low as $811.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Melbourne, Florida to Saint Petersburg as you normally would.