New Delhi, Jan 11 (IANS): The overall air quality in Delhi and adjoining areas continued to remain in the 'poor' zone on Thursday but the authorities have said that it is likely to fall again into the 'very poor' category on Friday.

"Air Quality Index (AQI) in Delhi is poor and it is likely to remain so until Thursday night. It will then again touch the lower side of very poor category due to decreasing wind speed," said System of Air Quality and Weather Forecasting and Research in its daily pollution analysis.

However, the agency has also predicted the air quality to improve again from Saturday due to a forecast of light rainfall over the weekend.

The overall AQI in Delhi at 4 p.m. was recorded at 292 (poor).

In the National Capital Region (NCR), Faridabad at 236, Ghaziabad at 298, and Noida at 290 also fared in the "poor" category.

However, Greater Noida, which on Wednesday had an AQI of 302 (very poor), improved to 'poor' on Thursday. Gurugram at 196 also improved to 'moderate' air quality, against Wednesday's poor air quality of 243.

The average concentration of PM2.5 and PM10 in Delhi was 154 and 261 microgrammes per cubic meters on Thursday. Across NCR, it was 144 and 254 units respectively.

Since the beginning of the year, the air quality in Delhi and adjoining areas have been oscillating between 'severe' and 'very poor' zone.

The AQI in Delhi dropped to the "severe" zone thrice in the first seven days of 2019. Although light rainfall during January 5 and 6 brought some relief to the national capital, the AQI still remained in the 'very poor' zone due to excessive moisture in the air.