Due to multiple factors, expect to potentially pay more when booking in December. For low rates, April can be a great choice for travel to South Africa. Flights to South Africa from Boise in April are about $1,348 on average during April, but can be found for as low as $963.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Boise to South Africa as you normally would.