Delhi's air quality improved marginally on Wednesday morning owing to favourable wind speed overnight but was recorded in the very poor category.

The overall air quality index stood at 323 at 8 am. However, calmer winds during the day may allow pollutants to build up.

A Met official said winds gusting up to 30 kmph barrelled through parts of Delhi for a brief period on Tuesday night. It helped improve the situation.

Delhi recorded a minimum temperature of 16.9 degrees Celsius, three notches above normal. The maximum temperature is likely to settle around 30 degrees Celsius.

Partly cloudy skies and very light rain are predicted during the day under the influence of a western disturbance affecting the hilly region in the north.

The improvement in air quality was evident from better visibility levels with 1,400 metres at the Palam airport and 1,500 at the Safdarjung airport.

A smoky haze had lowered the visibility levels to 800 metres at these places on Tuesday.

Favourable wind speed -- 15 to 20 kmph -- is predicted to bring a considerable improvement in the air quality from November 11.

The capital's 24-hour average air quality index stood at 372 on Tuesday. It was 354 on Monday, 339 on Sunday and 381 on Saturday.

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.

Farm fires in Punjab dropped from 2,487 on Monday to 605 on Tuesday. Their share in Delhi's PM2.5 pollution dipped from 14 per cent on Monday to nine per cent on Tuesday, according to data from the Indian Agricultural Research Institute and SAFAR, a forecasting agency under the Union Ministry of Earth Sciences.

The Delhi government had on Monday decided to reopen primary classes from November 9 and revoke the order asking 50 per cent of its staff to work from home in view of "improvement" in the city's air quality over the last few days.

However, plying of BS-III petrol and BS-IV diesel four-wheelers in Delhi will remain banned under stage 3 of the Graded Response Action Plan (GRAP).

Violation of the ban could invite a fine of Rs 20,000. Vehicles deployed for emergency services, and government and election-related work are exempted.

The Delhi government will run 500 additional buses in the capital under the "Paryavaran Bus Sewa" campaign to bolster public transport in a bid to reduce vehicular emissions.

According to a study conducted by The Energy and Resources Institute in 2018, vehicular emissions account for around 40 per cent of the PM 2.5 pollution in the capital.

With air pollution ameliorating in Delhi, the Commission for Air Quality Management (CAQM) on Sunday directed authorities to lift the ban on plying of non-BS VI diesel light motor vehicles in the region and the entry of trucks into the capital imposed under the stage 4 of the GRAP.

It had also banned construction work in public projects such as highways, flyovers, power transmission, and pipelines in Delhi-NCR.

The CAQM order recommending the restrictions was issued on Thursday.

According to an analysis conducted by the Delhi Pollution Control Committee last year, people in the national capital breathe the worst air between November 1 and November 15 when stubble burning peaks and winters set in.

The Air Quality Life Index (AQLI) released by the Energy Policy Institute at the University of Chicago (EPIC) in June showed that residents of Delhi stand to lose 10 years of life expectancy due to poor air quality.