Summer came early this year, like the last few years. By end of Feb, temperatures were already breeching 40. By end of Jan, the indications of summer were already there.
What changes with summer -
If they have AC, they turn those on (split units, no ventilaiton) https://twitter.com/Orla_Hegarty/status/1385490817192767491

With AC, to reduce bills, all doors, windows, ventilation louvres closed/blocked.
This is true for both residences and offices.
Malls with centralised AC start to recirculate more air as they try to cool more to attract more people - cooler shops are a status symbol.

Same with restaurants - AC on, keep at 18-20 C to show that yes we have AC for you to shelter from sun. This is again being used to attract customers inside where they can eat, with masks off.

Those who do not have AC, will still close the doors and windows especially from 10 am to 5 pm to avoid the glaring sun and the hot winds from outside.
This sets up the perfect environment for an #Airborne spread.