Visibility in the National Capital Region improved on Sunday, after two days of dense to very dense fog, the India Meteorological Department (IMD) said.

According to the railways, 23 Delhi-bound trains were running late from two to seven hours due to foggy conditions.

In Delhi, the IMD recorded shallow fog with a minimum temperature of 11.7 degrees Celsius, five notches above the season's average.

The city's Air Quality Index (AQI) was recorded at 388 in the 'very poor' category at 10 am.

According to the weather office, there was a significant improvement in visibility at the IGI Airport on Sunday. Runway Visual Ranges (RVRs) now range from 500 to 800 metres, indicating improved aviation conditions, it said.

The relative humidity stood at 91 per cent at 8.30 am.

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'.

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