The national capital witnessed moderate fog on Wednesday morning with the minimum temperature recorded at 11.2 degrees Celsius, three notches below the season's average, the India Meteorological Department (IMD) said.

Safdarjung observatory reported 400 metres of visibility while Palam observatory reported visibility of 500 metres at 7.30 am, it said.

Fog marring visibility below 50 metres is classified as very dense fog'. In the case of dense' fog, the visibility ranges from 50 metres to 199 metres, from 200 metres to 499 metres moderate , and visibility from 500 metres to 999 metres is considered as shallow' fog.

Delhi's air quality was in the very poor category' as the air quality index (AQI) at 7.05 am on Wednesday was 341, the Central Pollution Control Board data showed, whereas the AQI in its neighbouring areas such as Faridabad stood at 283, Ghaziabad (356), Greater Noida (216), Gurugram (274) and Noida (327).

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.

The weatherman has forecast shallow fog during the day and the maximum temperature is likely to settle at around 21 degrees Celsius.

The relative humidity at 8.30 am stood at 93 per cent, the IMD said.

On Tuesday, the maximum temperature settled at 20.8 degrees Celsius, a notch below the normal.