Kenya’s capital city, Nairobi, used to be known as the “Green City in the Sun” for its lush environment. There have been however recently been a lot of changes to Nairobi’s land cover – what’s on the ground’s surface. Research has found that an urban heat island is already manifesting over Nairobi. Data over Nairobi indicates that average air temperatures increased from 18.8°C in the 1950s to 19.5°C in 2000s. This situation is likely to become more pronounced given the ongoing environmental modification by construction, such as the Nairobi Expressway. Urban heat island refers to when temperatures in the city are higher than those of surrounding areas that have more vegetation cover. The effect is more pronounced at night when impervious surfaces re-radiate heat that is absorbed during the day into the atmosphere. This urban micro-climate will have an influence on the quality of life of city residents. Although the intensity of Nairobi’s heat island has not reached alarming levels of directly causing death, with ongoing developments this is bound to eventually happen.