With approaching winter, cities get covered by a lid, which is called inversion. Generally, the temperature inversion means an increase of temperature with altitude instead of the temperature getting colder.

Cold air is heavier than warm air so the cooler air stays close to the ground, while inversion at its upper limit prevents the air from mixing and heat from higher and warmer layers from reaching the ground.
With sufficient humidity, inversions are accompanied by fog or low clouds.
These low clouds can be observed in a Satellite layer as yellow clouds.

Acting as a lid, inversion traps pollutants released into the air by humans – combustion in industry, heating or transport. This can result in dangerously high pollutant concentrations, creating a smog situation.

Track the main air pollutants such as CO, NO2, SO2, and particulate matter PM2.5 and PM10 with Air quality stations. Together with Windy weather forecast data and real-time reported values, Windy users have a complete picture of the air pollution in their area.