Due to multiple factors, expect to potentially pay more when booking in August. For low rates, April can be a great choice for travel to San Juan. Flights to San Juan from Durban in April are about R20 051 on average during April, but can be found for as low as R15 844.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Durban to San Juan as you normally would.
Expect the weather to be around 32 °C on average in June. As the temperature peaks, try to get your plans done early, as flight price and availability will have an impact on your travels. The climate in San Juan is generally hotter than in Durban.