Johannesburg is located in the Southern Hemisphere. Therefore, its seasons are opposite to those in the Northern Hemisphere.
The coordinates (26° 08′ S, 28° 03′ E) confirm that Johannesburg is in the Southern Hemisphere, specifically in South Africa.
Answer: The average temperature in January is approximately 20°C, and in July it is approximately 15°C. This difference is due to Johannesburg being in the Southern Hemisphere, where January is a summer month and July is a winter month.