Lucknow, Jan 25 (IANS): Rail and air services were hit Friday as a thick fog blanketed many parts of Uttar Pradesh.

The fog, which began late Thursday, led to the cancellation of two flights -- the Lucknow-Delhi Indigo and Jet Airways flights. Hundreds of passengers were stranded at the airport; protests broke out against the airlines as passengers alleged they had been kept in the dark about the cancellations.

More than three dozen trains were also reported running late. These included Lucknow Mail, the New Delhi-Lucknow Shatabdi Express and the Chandigarh Express, all of which were late by over 10 hours.

The Met department confirmed the "return of extreme cold wave conditions".

The lowest temperature was recorded in Muzaffarnagar with 2.2 degrees Celsius.

Regional Met director J.P. Gupta said the chill was likely to continue for the next one week due to cold winds sweeping the state.

The sudden change of weather also led to electricity demand peaking, forcing the Uttar Pradesh Power Corporation Limited (UPPCL) to buy more power. With three consecutive holidays - Milad-un Nabi (Friday), Republic Day (Saturday) and Sunday - the corporation was buying 2,000 MW of additional electricity, an official said.