Delhiites woke up to the coldest morning of the season on Thursday with mercury plummeting to 2.2 degree Celsius.

The weather stations at Lodhi Road, Ayanagar and Ridge recorded the minimum temperatures of 2.8 degrees Celsius, 2.2 degrees Celsius and 2.8 degrees Celsius, respectively.

The national capital also witnessed very dense fog with visibility at a low of 25 metres at Palam and 50 meters at Safdarjung at 5.30 a.m, the India Meteorological Department said.

"Visibilities Reported at 0530 hrs IST of today, Jammu & Kashmir: Jammu 25, Punjab: Bhatinda 0; Amritsar, Patiala 25, Haryana, Chandigarh & Delhi: Ambala & Chandigarh, Palam 25 each; Safdarjung 50 Uttarakhand: Dehradun 200 Northwest Rajasthan: Ganganagar & Churu 25," the IMD said in a tweet.

The air quality of the National Capital remained in a very poor category with PM 2.5 at 325 and PM 10 at 195 under moderate category.

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'.

Experts said that the air quality may also remain in the very poor category for the next few more days.

At Pusa, the AQI recorded PM 2.5 at 313 which is a 'very poor category'.

At Lodhi Road, the Air Quality Index with PM 2.5 concentration was at 3o9 under the very poor category and the PM 10 stood at 184 under the moderate category. In Ayanagar the PM 2.5 was at 312, poor category while the PM 10 reached 186, in moderate category.

The Air Quality Index at the city's Mathura Road was also under the very poor category with PM 2.5 at 346 with PM 10 concentration at 277 under the poor category.

According to the forecast from the System of Air Quality and Weather Forecasting And Research (SAFAR), the air quality of the city will deteriorate further under the very poor category with PM 2.5 reaching 336 and the PM 10 concentration at 216 under 'poor category' on Friday.