India, Jan. 26 -- The mercury dipped to 3.6degC in parts of Delhi on Monday amid isolated cold wave conditions, even as the air quality deteriorated to the "poor" category following a rare, two-day streak of "moderate" pollution levels in January. An Average Air Quality Index (AQI) of 209 was recorded at 8am on Monday, compared to 153 at 4pm on Sunday, Delhi's lowest in January in four years.

Clear skies and sustained icy-cold northwesterly winds over the couple of days led to a further drop in temperature. A fresh western disturbance is expected to raise the mercury again and bring light showers on Tuesday.

A minimum temperature of 4.2degC, four degrees below normal, was recorded at Safdarjung, Delhi's representative weather observator...