Fog engulfed Delhi early Thursday morning, reducing visibility to as low as 400 mt, while there was no respite from cold with the mercury hovering around 4� C.

The fog cover did not hamper operations at the airport in Delhi, but continued to affect rail services with several trains reaching Delhi behind schedule and a few being cancelled.

The minimum temperature was recorded at 4.8� C, two degrees below normal, while the maximum was 22.3� C, a notch above normal, the Meteorological Department said. The British Broadcasting Corporation website had predicted sub-zero temperatures for Delhi this week.

All in-bound and out-going flights operated on schedule as the Runway Visibility Level at the airport remained above normal, sources said.

The trains cancelled included Farrukhabad-Bhiwani Kalindi Express, Allahabad-Ambala Unchahar Express, Delhi Sealdah Lal Quila Express and Toofan Express while those running late are Dibrugarh-Delhi Brahmputra Mail, Puri Hazrat Nizamuddin Kalinga-Utkal Express and Dharbanga-Delhi Shaheed Express.

Met officials said the mercury would hover around 5� C in the coming days and there would be an increase in night temperature.