Even as the sun shone bright and mercury climbed a few notches on New Year's Day in Lucknow, dense fog on the outskirts delayed a dozen trains and led to cancellation of five on Tuesday.

The trains cancelled include Bareilly-Allahabad Express, Chandigarh Express Special and Janta Express, a railway official said.

Many trains continue to run late by several hours.

Flights too have been disrupted. On Monday evening, two Indigo flights were cancelled due to poor visibility.

Airport officials said flight (6E-446) from Mumbai, which was to arrive here 7.30 p.m., was cancelled. A late evening flight from Lucknow to New Delhi (6E-449) was also cancelled due to fog.

A Met Department official predicted warmer day temperatures but colder nights and said cold waves were likely to return in the coming days.