[alien1993]

It's not really house heating fault, when the lockdown started everyone was at home and pollution actually went down; the strong winds those days certainly contributed to clean up the air too. And yes, those days was still cold, people were actually using heating.

Anyway the Pianura Padana is completely flat and surrounded by mountains east, north and south, the sea on the east doesn't help that much either with its winds. If you compare the shape of that red/black blob to a satellite image you can clearly see it traces the shapes of the mountains.

Count the fact that it's also heavily industrialized and populated and I guess you get why it's not like other industrialized regions.