The rains are caused by a depression in South-Western Bay of Bengal.
The climate agency said the rain spell is expected to last the whole week after the formation of low pressure in the southwest region near the Bay of Bengal.
The weather station at Lodhi Road, where the India Meteorological Department (IMD) headquarter is located, recorded a minimum temperature of 1.6 degrees Celsius.
Delhi saw cold wave conditions for the fifth consecutive day on Monday as very dense fog reduced visibility to just 25 metres, officials said.
The IMD said that the cold wave will prevail over many places of Delh-NCR between January 16 and 18. The minimum temperature at Ayanagar and Ridge may settle around 3 degree Celsius on Tuesday and Wednesday.
The IMD warned of an impact on agriculture, livestock, water supply, transport and the power sector at some places.
A Railways spokesperson said 36 trains were delayed by one to seven hours due to the foggy weather.
A blinding layer of dense fog over north India, including Delhi, caused major inconvenience to commuters.
The India Meteorological Department (IMD) said dense fog blanketed several parts of north India and the situation would continue in the coming weeks.
Sea surface temperatures remain warmer than average in the Western Pacific and around northern Australia which can result in greater humidity and rainfall.