Dense fog enveloped Delhi with visibility dropping to zero early Wednesday, as the minimum temperature dropped sharply to 7.4 degrees Celsius, the weather office said.

"Palam's visibility dropped to 50 metres at 12 midnight. It improved to 500 metres by 2.30 am, before dropping to zero at 5.30 am. Winds remained westerly at 5-7 kmph throughout the night," the India Meteorological Department (IMD) said.