@CPBRA
This high concentration of PM 2.5 is probably due to wildfires near north boarder. They are confirmed by NASA observation:
https://firms.modaps.eosdis.nasa.gov/map/#z:7;c:18.9,-7.5;d:2019-08-20..2019-08-21;l:firms_viirs=D,firms_modis_a
And shown by CO layer on Windy:
C646D707-B05E-453F-98E2-325C358D548E.jpeg
These fires increase the content of PM 2.5 as displayed in you post and also the NO2 as below:
4554EC90-9343-493A-AAF3-01AFE563037C.jpeg