It's absolutely crazy in Delhi, and the city is completely fogged out!

There is zero visibility in the national capital, with visibility dropped to just 50 metres, disrupting the movement of traffic.

Over 110 flights were affected at the Delhi airport after dense fog shrouded north India on Wednesday morning.

The weather office issued a red alert over "very dense fog" in the national capital as cold wave conditions continued. As many as 25 trains headed to Delhi are delayed, Northern railways said.

As roads remained engulfed in fog, several collisions were reported across Uttar Pradesh. One person was killed and 12 others injured after multiple vehicles collided on the Agra-Lucknow Expressway. In Bareilly, a speeding truck rammed into a house near the Bareilly-Sultanpur highway.

The India Meteorological Department (IMD) predicted "dense to very dense fog conditions" over Punjab, Haryana, Delhi, UP, Rajasthan and Madhya Pradesh.

In Delhi, the Palam observatory near the Indira Gandhi International Airport recorded a visibility level of 125 metres while at the Safdarjung observatory it dropped to just 50 metres. However, commuters reported even lower visibility in several parts of the national capital. Apart from Delhi, several north Indian cities woke up to foggy weather that reduced visibility. While Patiala, Lucknow and Prayagraj recorded very low visiblity of 25 metres, in Amritsar it dropped to 0 metres.

The air quality in the city also recorded a sharp decline after weeks of comparatively good air. The average air quality dropped to 381, "very poor" on the Air Quality Index.

The minimum temperature in Delhi was recorded at 7 degrees Celsius while the maximum temperature is expected to rise up to 24 degrees Celsius.