Due to multiple factors, expect to potentially pay more when booking in August. For low rates, February can be a great choice for travel to Bridgetown. Flights to Bridgetown from Boise in February are about $813 on average during February, but can be found for as low as $598.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Boise to Bridgetown as you normally would.