Due to a strong urbanization in Belgium, a lot of areas can be considered as particularly vulnerable to heat waves due to the urban heat island (UHI) effect. However, little information exists on the interaction between the urban heat island effects during heat waves and their interactions under present and future conditions. The heat wave definition and heat stress index chosen in this study are based upon the warnings issued by the Public Health of Belgium for the Brussels Capital Region. For this study, regional simulations were performed using the limited area model ALARO, coupled with the Town Energy Balance scheme. The offline air quality simulations are calculated using the CHIMERE model. Results from our observations and climate simulations indicate that for the present climate conditions night time UHI is enhanced during heat waves which affects also urban and rural surface energy balance differently. The projected climate change under scenario A1B for 2050 leads to an increase of the number and duration of heat waves. More specifically, for rural (urban) areas, climate change increases the intensity of heat waves more during the day (night). We will also look more closely to the effect these changes have on air quality when taking the present and future climate scenarios under consideration. There is a significant increase in the number of days for which ozone concentrations exceed the warning threshold during heat waves. Besides the urban scale we will also investigate the impact of this configuration on air quality for the rural scale under present and future climate conditions.