The national capital on Saturday recorded its coldest day of the season as the minimum temperature plummeted to 2.4 degrees Celsius in the morning. The mercury even plunged to below two degrees Celsius in some areas with the Lodhi Road Observatory recording a low of 1.7 degrees Celsius. The Safdarjung Observatory, whose reading is considered the official marking for the city, recorded 2.4 degrees Celsius in the morning. Palam recorded 3.1 degrees Celsius and Aya Nagar 1.9 degrees Celsius. The falling temperatures, high humidity and low wind speed meant that the air quality turned severe again on Saturday. The overall air quality index stood at 413 at 10 am.