I too observed the air quality index levels in my mobile, which continued to be high in the night and early hours, though, not high compared to daytime levels.
Another observation is the formation of a fine dust layer on the vehicles parked in garages and inside the houses after a few hours, even after wiping the surfaces in the night.
This indicates poor air that may not be suitable for us even in early morning hours and we can't go for outdoor exercises, particularly in winter. We may also get into respiratory problems by inhalation of condensed moisture as particulate matter. Maybe we have to cover the face with masks to avoid inhalation of harmful matter, not thinking that it is safe as there is no vehicle movement on the roads.