The national capital witnessed shallow fog on Wednesday morning and recorded minimum temperature of 8.4 degrees Celsius, a notch above the normal, with the weather office predicting a cloudy day.

The India Meteorological Department (IMD) said that the city received 4 mm of rainfall in last 24 hours between 8.30 am on Tuesday to 8.30 am on Wednesday.

"There will be generally cloudy sky with shallow to moderate fog on Wednesday," IMD officials said.

The relative humidity at 8.30 am was 97 per cent in Delhi, IMD said.

The maximum temperature of the day is likely to hover around 20 degrees Celsius.

The maximum temperature on Tuesday settled at 18 degrees Celsius, three notches below the normal.

The city's air quality improved to "poor" category on Wednesday as the air quality index (AQI) at 8 am was 288, the Central Pollution Control Board (CPCB) data showed.

On Tuesday, the air quality was in "very poor" category as the 24-hour AQI of Delhi read 305 at 4 pm.

The AQI of its neighbouring cities -- Faridabad (284), Ghaziabad (286), Gurgaon (264) -- were in poor category.

However, the AQI in Greater Noida (307) and Noida (305) was recorded in the very poor category at 8 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.