How to cool during heatwaves

Under a warming climate intense heatwaves are expected that would stay for hours, days, weeks and months.  It becomes even worse under urbanization - the more cities grow , the  more natural land covers such as vegetation and soil are replaced by impervious surfaces such as concrete, asphalt roads and buildings. These impervious  urban surfaces can't retain water much longer like soil and vegetation and this would exacerbate the heating further.  Urban heat islands add more than 3 deg. C (Fig. 1) to the heatwaves. The combined effects of heatwaves and urban heat islands are heat-related illnesses and death - specifically affecting young toddlers and old people because their body regulation mechanism is lower.

Figure 1. Urban heat island adds more than 3 deg. C to the heatwaves and increases the frequency or duration of the heat.

Under a warming climate, it is only a matter of time before we start to seek for cooling mechanisms both for short term and long term. Heatwaves also have the tendency to accumulate pollutants into few areas - increasing its dose in only few particular places than regulated. Because wind is usually weak during heatwaves and there is less mixings and dispersal. The accumulated air pollutants are dangerous and cause breathing difficulty especially to children and old people. So, if there is heatwave warning in your area, you should constantly monitor your breathing rate and your heart beats while moving in the cities during heatwaves.
If you feel breathing difficulties and if you think your heart beat is abnormal you need to find cooling sites immediately. Breathing inconveniences can also arise because of air pollution, so you should leave the area immediately. Parents are also advised to monitor their children continuously. It's better to stay in cool places such as air conditioned houses, vegetated areas such as parks, places where there are cool water sprays.

In such situations, you can consider some of the short term cooling methods:
a) Heating, ventilation and air-conditioning systems (HVACs) - this method is ususally used indoors.

b) cool water sprays and fountains
                         (i) fountains

                             (ii) Water sprays on asphalt roads

                               (iii) water spray fans

c) vegetation that cover dormitories and apratment buildings

The long-term solutions are starting aggressive projects of reforestation in the city, roof top lightening and gardening, planning future urban development  for optimal distance among buildings to increase shadows and increase ventilation, reduce motor vehicle circulation, constructing urban ventilation corridors through which cool air flows towards the center of the cities from lakes, rivers nearby, converting parking lots into green/forested areas,  and  constructing cool water flow channels through the cities. City municipalities can implement one or more of the above to reduces the impact of heatwaves and urban heat islands on population and infrastructure.