Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from OR Tambo to Djerba as you normally would.
This flight path from Johannesburg OR Tambo to Houmt Souk Melita was viewed by 11 users in the past month. Keep an eye out for changes in search interest prior to high and low season.
When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Johannesburg is roughly greater than that of Djerba. You can assume this to be the case over the next 19 days.
We forecast the temperature to be around the 37 °Cs in August, on average. The temperature in Djerba is generally hotter than in Johannesburg. Book flights in a timely manner in correlation to your departure date.