At 9 am on Saturday, moderate fog enveloped parts of Delhi, registering the lowest visibility at 200 meters at Safdarjung, the primary weather station in the capital, according to the Indian Meteorological Department (IMD).
Palam maintained visibility above 500 meters, minimizing the impact on flight operations compared to previous days.
IMD categorizes fog as ‘shallow’ when visibility ranges from 500 to 1000 meters, ‘moderate’ between 200 and 500 meters, ‘dense’ between 50 and 200 meters, and ‘very dense’ when it is below 50 meters.
Concurrently, Delhi’s air quality deteriorated to the upper limit of the ‘very poor’ category and is anticipated to reach ‘severe’ later in the day. The 24-hour average Air Quality Index (AQI) was very poor at 382 at 4 pm on Friday, further worsening to 399 at 9 am on Saturday. An AQI exceeding 400 is designated as ‘severe.’
On Saturday, the Indira Gandhi International Airport (IGIA) reported no cancellations or diversions, although about 10 flights experienced delays in the early hours. Meanwhile, the Northern Railway reported delays of more than one hour for at least 30 trains to and from Delhi.
The IMD had forecast the likelihood of moderate to dense fog across the capital on Saturday, with a yellow alert in place for similar weather on Sunday. Upper-level fog on Friday resulted in Delhi’s maximum temperature falling below 20 degrees Celsius for the first time this season.
The capital’s maximum temperature recorded was 19.8 degrees Celsius, one degree below the normal for this period. The IMD projects Delhi’s maximum temperature to hover around 18-19 degrees Celsius on Saturday and Sunday, with isolated areas potentially experiencing ‘cold day’ conditions.
A ‘cold day’ is classified when the maximum temperature is 4.5 degrees Celsius or more below normal, with the minimum also below 10 degrees Celsius. While the maximum criteria were met at some stations, the minimum temperature at Safdarjung was recorded at 10.7 degrees Celsius on Friday, four degrees above normal. On Saturday morning, Safdarjung recorded a minimum temperature of 11.8 degrees Celsius. Senior scientist Kuldeep Srivastava explained that the persistent layer of fog raises nighttime temperatures as heat becomes trapped, contributing to colder days with narrowed gaps between maximum and minimum temperatures.
