Trains were running late and flight schedules were disrupted due to fog returning in Uttar Pradesh Tuesday.
Jet Airways and Indigo, which had cancelled their early morning flights till Jan 28, have now extended this to Jan 31, officials said.
The only morning flight now available for passengers is Air India (AI412) between New Delhi and Lucknow.
The weatherman predicted that fog would stay for two days and the sun will only show up past noon.
More than a dozen trains were running late.
The maximum temperature in Lucknow Monday was 21.6 degrees Celsius, two degrees below average. The minimum temperature was 12.8 degrees Celsius, two degrees below average.
Icy winds from the Himalayas are also compounding the weather woes, the Met Office said.