A cold wave gripped Delhi on Wednesday as frosty winds from the snow-clad western Himalayas continued to sweep the plains and brought the minimum temperature down to 3.2 degrees Celsius, the IMD said.

"Dense" fog blanketed parts of the city, lowering visibility to 50 metres and affecting traffic movement.

Cold wave conditions prevailed at the Safdarjung Observatory, which provides representative data for the city. It recorded a minimum of 3.2 degrees Celsius, four notches below the normal, said Kuldeep Srivastava, the regional forecasting centre head of the India Meteorological Department (IMD).

In the plains, the IMD declares a cold wave if the minimum temperature dips to 4 degrees Celsius. A severe cold wave is when the minimum is 2 degrees Celsius or less.

Cold and dry northerly/northwesterly winds from the western Himalayas have been barrelling through the plains, bringing down the minimum temperature in north India, Srivastava said.

Similar conditions will prevail in the city over the next two days, he said.

"Dense" fog lowered visibility to 50 metres at Palam and 200 metres at Safdarjung, the IMD said.

According to the IMD, a "very dense" fog is when the visibility is between 0 and 50 metres. In case of a "dense" fog, the visibility is between 51 and 200 metres, "moderate" 201 and 500 metres, and "shallow" 501 and 1,000 metres.

Delhi had been registering above-normal minimum temperatures till Monday, as a cloud cover persisted over the city under the influence of successive Western Disturbances (WDs).

However, the temperature started dropping with the commencement of cold northwesterly winds after the withdrawal of the latest WD.

The city's minimum had settled at 4.8 degrees Celsius on Tuesday, 7 degrees Celsius on Monday, 7.8 degrees Celsius on Sunday, 10.8 degrees Celsius on Saturday, 9.6 degrees Celsius on Friday and 14.4 degrees Celsius on Thursday, the highest in January in four years, according to the IMD.