New Delhi, Dec 18 (IANS): Delhi is likely to experience toxic air over the next two days as weatherman on Tuesday predicted the already "very poor" quality of air of the national capital will deteriorate further.

"Feeble western disturbance over the northern part of India, fall in temperature, moisture and moderate fog is likely to increase both gaseous and particulate pollutants for the next two days," System of Air Quality and Weather Forecasting and Research (SAFAR) said in its daily forecast.

However, the agency said the pollutants will over the next two days reach the upper level of the "very poor" zone and then gradually decline.

The overall Air Quality Index (AQI) of Delhi at 4 p.m stood at 353 (very poor). In the National Capital Region (NCR), Greater Noida at 373, Ghaziabad at 363, Faridabad at 326 and Noida at 323 also remained in the "very poor" zone.

However, Gurugram, which had been maintaining "moderate" level of air quality for some days, also slipped into the "poor" category with an AQI of 221.

An AQI between 201 and 300 is considered "poor", 301 and 400 "very poor" and 401 and 500 "severe".

As per the data of the Central Pollution Control Board (CPCB), the average concentrations of PM2.5 and PM10 in Delhi at 7 p.m were 204 and 347 microgrammes per cubic metres, respectively. Across NCR, it was between 189 and 332 units, in same order.

While the overall AQI of Delhi remained in the "very poor" zone, districts like Mundka, Nehru Nagar, Jahangirpuri and Mathura Road recorded "severe" levels of PM2.5 (ranging between 401 and 500).

According to the India Meteorological Department (IMD), minimum temperatures are likely to fall further by 1-2 degrees Celsius in the next two days in the plains of northwest India.

For Wednesday, the IMD has forecast a clear sky with shallow fog in the morning. "The maximum temperature on Wednesday is likely to hover around 22 degrees Celsius, while the minimum would remain around 5 degrees, three notches below the season's normal," an IMD official told IANS.