Due to multiple factors, expect to potentially pay more when booking in July. For low rates, October can be a great choice for travel to Johannesburg OR Tambo Airport. Flights to Johannesburg OR Tambo Airport from Chicago Midway Airport in October are about $976 on average during October, but can be found for as low as $704.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Chicago Midway Airport to Johannesburg OR Tambo Airport as you normally would.