After a two-day gap, Delhi's air quality plunged into the "very poor" category again on Sunday, as winds in the national capital that improved pollution levels the last couple of days lost its speed.

At 9 am, Delhi's Air Quality Index (AQI) was recorded at 359, a marked increase from Saturday's reading of 255, according to data from the Central Pollution Control Board (CPCB).

Data from 36 out of 40 monitoring stations was shared by the department. Among these, eight stations -- Anand Vihar, Alipur, Bawana, Jahangirpuri, Mundka, Wazirpur, Vivek Vihar and Sonia Vihar have AQI readings in the "severe" category, while the remaining 28 are in the "very poor" 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'.

According to the India Meteorological Department (IMD), wind speed in the city was calm at 0 kmph. Delhi's air quality had improved from 'very poor' to 'poor' category the last two days due to favourable winds.

A layer of smog blanketed the city in the early hours on Sunday, making visibility difficult.

The minimum temperatures were recorded at 20.1 degrees Celsius, one notch above the season's average.

The IMD reported a humidity level of 93 per cent in the morning.

The weather department has forecasted predominantly clear skies throughout the day, with the maximum temperature expected to reach around 33 degrees Celsius.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.