The visibility went down to less than 100 metres Monday night and many trains were delayed by several hours. Over a dozen flights from Lucknow to Delhi and Mumbai were cancelled.
Airport officials said all major flight operators - Indigo, Jet Airways, Spice Jet and national carrier Air India, were hit by inclement weather and had to cancel their flights due to poor visibility.
Railway officials said more than 40 trains were running behind schedule, out of which more than a dozen trains were running late by 12-14 hours.
Important trains hit by fog delays include the superfast Duronto Express, Rajdhani Express and the Shatabdi Express, running between New Delhi and Lucknow.
Due to the delay in schedule of trains, the Charbagh railway station in Lucknow was overcrowded and chaos prevailed on most platforms.
Road traffic, including the Uttar Pradesh Roadways buses, moved at snails pace with visibility being very poor, a state roadways official said.
Night bus travel was worst hit.
The maximum day temperature recorded in the state capital was 18 degrees Celsius, four degrees below the season's normal, while the night temperatures hovered around 9 degrees Celsius, two notches below normal, according to the Met Office said.