Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from North Carolina to Sri Lanka as you normally would.
Due to multiple factors, expect to potentially pay more when booking in August. For low rates, March can be a great choice for travel to Sri Lanka. Flights to Sri Lanka from North Carolina in March are about $1,346 on average during March, but can be found for as low as $1,081.