New Delhi, Jan 1 A heavy blanket of fog engulfed the national capital region on the New Year on Monday with the visibility dropping to zero. A large number of flights and trains were delayed. The minimum temperature was recorded at 5.7 degrees Celsius, a notch below the season's average. A shallow fog would continue throughout the region all through the day, the Met said. The visibility which was 1,500 metres at 3.30 a.m. dropped rapidly to zero at 5.30 a.m. The maximum temperature was likely to hover around 23 degrees Celsius, an India Meteorological Department said. The humidity at 8.30 a.m. was 100 percent. Sunday's maximum temperature settled at 23.9 degrees Celsius, while the minimum was recorded at 6.4.