Delhi is likely to witness cold day conditions at isolated places on Thursday, with the city registering a drop of three degrees in the minimum temperature at 6.3 degrees Celsius, the weather office said.

According to weather officials, the city has been reeling under cold day conditions for the last three to four days due to rains, fog and little exposure to the sun.

Tuesday was Delhi's coldest January day in nine years, with the maximum temperature plunging to 10 degrees below normal and settling at 12.1 degrees Celsius.

Before this, January 3, 2013 had recorded a maximum temperature of 9.8 degrees Celsius, according to India Meteorological Department (IMD) data.

It was also the second consecutive "severe cold day" in the national capital. Wednesday was also a cold day.

According to IMD, a "cold day" is when the minimum temperature is less than 10 degrees Celsius and the maximum is at least 4.5 degrees Celsius below normal.

A "severe cold day" is when the maximum temperature is at least 6.5 notches below normal.

There will be mainly clear sky. The city will witness cold day conditions at isolated places on Thursday, the IMD forecast said.

It said that maximum temperature of the day is likely to hover around 17 degrees Celsius.

The maximum temperature on Wednesday had settled six notches below the season's average at 16.4 degrees Celsius.

The relative humidity at 8.30 am on Thursday was 97 per cent, the weather office said.

Delhi's air quality was in poor category as its air quality index (AQI) at 8 am on Thursday was 264, the Central Pollution Control Board data showed.

An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.