Delhi sees season's first fog; air quality enter poor category by weekend

Delhi reported the season's first episode of fog on Wednesday morning which lowered visibility levels to 350 metres in some parts of the capital.

The city recorded a minimum temperature of 20.2 degrees Celsius, a notch below the normal. The maximum temperature settled at around 31 degrees Celsius.

Senior scientist at the India Meteorological Department (IMD) R K Jenamani said the increased moisture content in the air due to a prolonged spell of rain and low temperatures led to the formation of moderate fog in Delhi.

"This is the capital's first fog of the season," he said.

According to the IMD, very dense fog is when visibility is between 0 and 50 metres, 51 and 200 is dense, 201 and 500 moderate, and 501 and 1,000 metres shallow.

Another IMD official said visibility at the Safdarjung Observatory, Delhi's primary weather station, had dropped to 600 metres and to 350 metres at the Palam weather station at 8.30 am.

This improved to 2,100 metres at Palam by 9 am and at Safdarjung by 10 am.

Locally generated pollutants and fog pushed the air quality in the city from the "satisfactory" category to the "moderate" category.

The 24-hour average air quality index stood at 143. It was 66 on Tuesday and 44 on Monday, 48 on Sunday, 56 on Saturday and 55 on Friday.

The air quality is likely to deteriorate to the poor category by Saturday (October 15).

Favourable weather conditions, rains and strong winds, over the last five days suppressed incidents of stubble burning in Punjab and Haryana and kept the air in Delhi-NCR clean.

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'.