India, May 15 -- Visibility dipped and the air quality deteriorated to the "poor" category in Delhi and the National Capital Region (NCR) due to overnight dust-raising winds, the India Meteorological Department (IMD) said on Thursday. The IMD added that a gradual improvement was expected through the day.

The average Air Quality Index (AQI) was in the "poor" category on Thursday, primarily due to the dust, which spiked the PM 10 concentration. The average AQI was 249 (poor) at 9am compared to 135 (moderate) a day earlier.

IMD senior scientist RK Jenamani said the dust-raising winds were reported around 10pm on Wednesday. He added that the visibility dipped from 4,500 metres to 1,200 metres. "There were sudden gusty winds of 30-40 km/hr.....