UHI (Urban Heat Island) refers to the elevated temperatures in developed areas compared to more rural surroundings and is of increasing concern, especially in the light of global warming and because of an increasing population in cities.
The figure on the right illustrates the Paris Urban Heat Island effect during the summer of 2003. The summer (May-June-July-August) average air temperature at 22:00 GMT is shown. Compared to the rural surroundings, the air temperature in the city center is on average 5 degrees warmer. On particular days, this can be several degrees higher.
In 2013, VITO measured the UHI effect for the city of Antwerp by means of 2 monitoring stations, one at the rural countryside and one located in the city centre. The image above shows the daily maximum air temperature difference between the 2 locations which corresponds to the UHI-effect. A large day-to-day variability is visible with maximum values up to 8 degrees Celcius.