Dense fog covered Delhi on Sunday as a biting cold wave strengthened its hold on the city. As a result, visibility dropped sharply in many areas during the early morning hours, affecting daily movement.

At the same time, Delhi continued to battle extremely poor air quality. At 8 am, the Air Quality Index stood at 440, placing it firmly in the ‘severe’ category. Therefore, authorities enforced Stage IV of the Graded Response Action Plan (GRAP) from Saturday, the toughest level of pollution control.

Temperatures remain low as IMD issues warning

Meanwhile, temperatures stayed low across the capital. Delhi recorded a minimum temperature of 5 degrees Celsius, while the maximum reached 22 degrees Celsius. Because of the cold and foggy conditions, the India Meteorological Department (IMD) issued a yellow alert for January 18.

Safdarjung recorded the lowest temperature at 5.3 degrees Celsius. In comparison, Palam reported 8 degrees. Lodi Road saw a minimum of 6.8 degrees, while both the Ridge and Ayanagar recorded 7.2 degrees Celsius.

Visibility falls sharply across Delhi and north India

Due to thick fog, visibility dropped to alarming levels in several areas. According to the IMD, Safdarjung reported zero visibility, while Palam recorded visibility of only 100 metres.

Similarly, fog affected many parts of north India. Bareilly, Lucknow, and Kushinagar also reported zero visibility. Meanwhile, Amritsar and Gorakhpur recorded visibility of 100 metres, and Prayagraj reported visibility of 200 metres.

Airlines issue advisories amid foggy conditions

As fog reduced visibility, several airlines issued advisories to passengers. Air India and IndiGo warned travellers to expect delays and advised them to check flight updates regularly.

Passenger Advisory issued at 07:00 hrs.

Please click on this link for real-time winter travel updates: https://t.co/Y0B6lhwIj4#DelhiAirport #PassengerAdvisory #DELAdvisory pic.twitter.com/cYl61QLd1j

— Delhi Airport (@DelhiAirport) January 18, 2026

However, at 8 am, the Delhi airport said, “ All flight operations are normal.”

IndiGo and Air India caution passengers

IndiGo issued an advisory stating that fog and low visibility over Delhi and Hindon airports could disrupt flight schedules.

Travel Advisory

Low visibility and fog over #Delhi and #Hindon (Airport) may impact flight schedules. We are closely monitoring the weather and doing our best to get you where you need to be, safely and smoothly.

We request that you stay updated on your flight status via our…

— IndiGo (@IndiGo6E) January 17, 2026

Similarly, Air India warned passengers about dense fog and reduced visibility across parts of north India, including Delhi. The airline said such conditions could cause delays and disruptions across its flight network.

#TravelAdvisory

Reduced visibility due to dense fog is forecast in parts of Northern India, including Delhi, tomorrow morning. These conditions may have a cascading impact on flight schedules across our network.

We understand how important your travel plans are and have taken…

— Air India (@airindia) January 17, 2026

GRAP Stage IV restrictions enforced again

As air quality remained severe, GRAP Stage IV restrictions returned in Delhi. Under these rules, authorities restricted the entry of BS-IV truck traffic into the city. In addition, they halted all construction and demolition activities.

Moreover, schools up to Class 10 must shift to hybrid classes. Only Classes 10 and 12 can continue with in-person learning.