More than 25 percent of Africa is desert. Sahara is not the only desert in Africa.
Checked the forecasts of 10 largest cities in Africa, lowest avg. daily temperatures in Jan/July in Celsius.
Lagos: 30/26
Kinshasa: 27/29
Cairo: 18/34
Johannesburg: 24/14
Khartoum: 29/35
Dar es Salaam: 30/24
Alexandria: 16/26
Abidjan: 29/25
Algiers: 13/28
Kano: 21/26
The 4 sub-20 cities are either coastal cities or very close to the coast, those away from seas/oceans are what can be accurately described as "hot".
> most of sub-saharan africa has moderate temperatures
That climate map is deceptive. It may lead you to believe that "blue" areas are very cool, yet Kinshasa is in Congo, the country with the most blue/deep blue color on that climate map.
Kindu, a 172 000 town closest to the deep blue area on that map is 24/28, not the coolest place on Earth.