Dense fog engulfed large swathes of north India reeling under intense cold as visibility reduced significantly, disrupting rail services and causing a vehicle pile-up in Uttar Pradesh on Wednesday.
The harshest winter period 'Chilla-i-Kalan' also set in Kashmir freezing fringes of many water bodies.
At least 11 people were injured in the pile-up involving several vehicles on the Lucknow-Gorakhpur National Highway, even as a moderate fog cloaked Delhi where 18 trains were running late by 1:30 to five hours.
Operations at the Delhi airport remained normal. However, three flights were returned or diverted to the Delhi airport due to bad weather in Chandigarh, Varanasi and Lucknow on Tuesday night.
Amid low temperatures, high moisture and still winds, a layer of dense to very dense fog persisted over Punjab, Haryana, northwest Rajasthan, Uttar Pradesh, Bihar and parts of Uttarakhand, according India Meteorological Department.
At 5:30 am, visibility levels stood at zero in Bhatinda; 25 m in Ganganagar, Amritsar and Bareilly, and 50 m in Varanasi, Bahraich and Ambala.
In a statement issued at 1:30 pm, the IMD said dense to very dense fog in many/most pockets is very likely over Punjab, Haryana, Delhi and Uttar Pradesh during night and morning hours in the next 24 hours due to moisture and light winds at lower tropospheric levels over the Indo-Gangetic plains.
According to IMD, very dense fog is when visibility is between 0 and 50 metres, 51 and 200 is dense, 201 and 500 moderate, and 501 and 1,000 shallow.
The Sadarjung Observatory, the primary weather station in Delhi, recorded a minimum temperature of 7.1 degrees Celsius, a notch below normal.
The maximum temperature settled at 21.2 degrees Celsius, the lowest so far this season.
The minimum and maximum temperatures are likely to drop to 5 degrees Celsius and 20 degrees Celsius in the next few days.
On the Lucknow-Gorakhpur National Highway, a bus overturned after colliding with a truck which led to the pile-up of more than 12 other vehicles. As many as 11 people in vehicles behind the bus were injured.
A day earlier, two persons were killed and 15 injured in separate accidents amid low visibility due to dense fog in different districts of Uttar Pradesh.
A dense fog also enveloped several places in Uttar Pradesh on Wednesday morning with people across districts braving a severe cold with dropping night temperature.
According to the report of the Meteorological Centre, Lucknow, most areas in the eastern and western parts of the state witnessed fog in the morning and a drop in temperature.
During the last 24 hours, a significant drop in day temperature was recorded in Moradabad and Meerut divisions of the state, it said.
Prayagraj, Bareilly, Moradabad, Ayodhya, Kanpur, and Bareilly too saw a drop in day temperatures.
Fursatganj was the coldest place in the state in the last 24 hours with temperature there dropping to 4.9 degree Celsius.
In the next 24 hours, a dense fog is expected in the morning and evening in Maharajganj, Siddharthnagar, Gorakhpur, Kushinagar, Deoria, Sant Kabir Nagar, Saharanpur, Muzaffarnagar, Amroha, and Bijnor.
Kashmir's harshest winter period 'Chilla-i-Kalan' began on Wednesday with the mercury dropping several notches below the freezing point at many places including Pahalgam, which recorded the lowest night temperature at minus 6.2 degrees Celsius.
'Chilla-i-Kalan' is a 40-day period when a cold wave grips Kashmir and temperatures drop considerably.
'Chillai-Kalan' will end on January 30. The cold wave continues even after that in Kashmir with a 20-day 'Chillai-Khurd' (small cold) and a 10-day 'Chillai-Bachha' (baby cold).
Several places in Kashmir witnessed their coldest nights of the season so far. The fringes of many water bodies, including the Dal Lake here, froze as did water in taps, the officials said.
Srinagar recorded a minimum temperature of minus 4.2 degrees Celsius last night, they said.
The famous ski resort of Gulmarg in north Kashmir's Baramulla district recorded a low of minus 4.6 degrees Celsius.
The mercury settled at a low of minus 4.4 degrees Celsius in north Kashmir's Kupwara, minus 4.2 degrees Celsius in Qazigund and minus 2.4 degrees Celsius in Kokernag.
The meteorological department has forecast mostly dry weather in Jammu and Kashmir till December 24.
There is possibility of rains or light snowfall in some parts of Kashmir around Christmas, it said.
Officials said in a first, Sinthan Pass-- connecting Kashmir to Chenab valley in Jammu region, has been kept open for tourists as well as locals on the first day of Chillai Kalan.
The road also helps maintain connectivity of Jammu and Kashmir divisions when NH 44 is blocked due to adverse weather, they said.
