Foggy conditions persisted in most parts till early morning hours but a peculiar aspect was noticed in Delhi. Fog in Delhi and NCR started setting in quite late at night and gradually became dense. General visibility remained below 50 meters for about 3 hours and dropped to nil at 3.30 am. Thereafter, fog dissipated and visibility improved to 1.4 km around 4 am.
On the other hand, Amritsar witnessed dense fog on Wednesday morning. Allahabad, Varanasi and Lucknow reported nil visibility. Gorakhpur and Patna observed visibility up to 100 meters. Jaipur and Agra also reported shallow fog, with visibility of 500 meters and 600 meters, respectively.
Early dissipation of fog in Delhi could be attributed to the change in wind pattern. Midnight onwards predominantly southeasterly winds blowing over the region led to dispersion of fog and the weather cleared up in the morning.
In the view, these moist winds blowing at about 15 to 20 kmph allowed a significant fall in temperatures as well. Irrespective of direction, speed of wind also plays a deciding factor in dissipation or sustenance of fog in a particular place. Fog starts dispersing as soon as the winds start blowing at a speed of more than 5 kmph. There was hardly any drop in temperature after 10 pm on Tuesday and the minimum recorded on Wednesday morning was 8.6°C.