Mumbai's Bandra Kurla Complex experienced a moderate smog layer with an AQI of 123. Meanwhile, Delhi grappled with hazardous air quality, reaching a severe 391, with several areas exceeding 400. Cold weather and calm winds are trapping pollutants, causing widespread haze. Authorities are implementing measures like 'No PUC, No Fuel' and Stage IV GRAP actions to combat the worsening air.