Massive heat waves like the ones observed in Canada and the U.S. right now are a result of different factors working together forcing the weather system into an extreme condition. For the moment, the meanders of the jet stream are the main elements responsible for this heat drama, generating a so-called “Omega” weather situation. Like in the Greek letter, the “Omega” condition causes a large recirculation and stagnation of overheated air over Canada. In this ever-returning air mass, heat builds up from day to day.
Long term, changes in land use and the effect of climate change will cause more frequent alterations in the tropospheric jet stream leading to unusual and extreme weather conditions. All components of our system will be heavily impacted by such conditions, but urban areas add another source of extra heat to this already overloaded system.
It is therefore extremely important to design our cities in a way to avoid such heat accumulation and, in addition, to provide cool spots accessible to everyone in the case of heat waves.