Delhi experienced severely polluted air on December 28, with AQI levels reaching 391 and bordering the 'Severe' category. Thick smog enveloped the city, reducing visibility and impacting multiple areas, including Akshardham and Anand Vihar, which recorded 'Severe' AQI. Unfavorable weather conditions, including cold temperatures and fog, exacerbated the persistent winter pollution across the National Capital Region.