It was a cold Christmas morning in the national capital on Monday as a thick layer of fog covered the city while the air quality improved from the "severe" to the "very poor" category, officials said.

The minimum temperature settled at 9.4 degrees Celsius, the India Meteorological Department said.

The relative humidity at 8.30 am stood at 100 per cent.

Delhi's air quality index (AQI) showed minor improvement on Monday morning.

The AQI at 9.05 am stood at 393. The 24-hour AQI was 411 on Sunday.

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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