Thick fog blanketed Delhi early Tuesday, reducing visibility and delaying 25 trains. The city recorded a minimum temperature of 10.5 degrees Celsius.

"Minimum visibility of 150 metres in dense fog with northwesterly winds at 11-13 kmph was reported over Palam between 5 and 5.30 am, gradually improving to 700 metres in shallow fog with westerly winds at 13 kmph by 8.30 am," the India Meteorological Department (IMD) said.

At Safdarjung, the minimum visibility was 500 metres, it said.

Due to the foggy weather, a total of 25 trains were delayed till 6 am, an official said.

The minimum temperature in Delhi increased marginally to 10.5 degrees Celsius, 3.6 notches above normal, from 9.6 degrees Celsius on Monday, according to the IMD.

The humidity level was 92 per cent at 8.30 am.

The weather office has forecast very dense fog during the day with the maximum temperature expected to settle around 19 degrees Celsius.

Delhi's Air Quality Index (AQI) remained in the 'very poor' category with a reading of 303 at 9 am, according to the Central Pollution Control Board.

An AQI between 0 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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