The last major cold wave struck north India in January 2013. That year, Delhi’s temperature dropped to 1.9°C, its lowest in 44 years, claiming 237 human lives.
Large parts of Uttar Pradesh, Bihar, and Punjab recorded near-freezing conditions. At least 170 people died in Uttar Pradesh alone.
Even before the full onset of winter, the Indian Meteorological Department (IMD) has predicted that it is expected to be a colder–than–usual season.
What is driving a harsh winter ahead? How will that impact pollution? The Quint explains.
Colder-Than-Usual Winter Could Worsen Pollution Across North India, Warn Experts
1. What’s Driving India’s Harsh Winter Ahead?
K Venkatramana, fellow at The Energy and Resources Institute (TERI), explains to The Quint that the IMD's projections of a colder winter are based on a mix of factors, which together allow cold air to linger over India longer than usual.
The influence of La Niña
Jet stream shifts
Regional ocean warming
La Niña is a climate event where cooler waters in the Pacific Ocean alter global wind and weather patterns.
"During this episode, India often experiences more frequent and longer cold waves."
K VenkatramanaIndia has already witnessed the consequences of La Niña this year. In early October, north and northwest India saw sporadic showers, which lowered temperatures in the plains.
The Himalayas also received an early snowfall, along with isolated hailstorms in Jammu, western Rajasthan, and western Uttar Pradesh in early October.
Vishal Dixit, climate scientist and assistant professor at the Centre for Climate Studies, IIT Bombay, tells The Quint that the reason for these sporadic showers and early snowfall in the Himalayas is a consequence of the storm tracks over the Mediterranean and the western Himalayas becoming active due to the shift in jet streams caused by La Niña.
Furthermore, the warming of the Arabian Sea along with these changes prolong the cold wave conditions over north India.
According to the US-based NOAA Research, a research and development body to enable better forecasts, earlier warnings for natural disasters, and a greater understanding of the earth, a cycle of warm El Niño and cool La Niña episodes that happen every few years in the tropical Pacific Ocean is "the most dramatic year-to-year variation of the earth’s climate system, affecting agriculture, public health, freshwater availability, power generation, and economic activity" around the global.
Expand2. Colder Winters Likely to Worsen Air Pollution Across India
As India prepares for a colder winter, Professor Abhijeet Chatterjee of Bose University, Kolkata, warns that this could further lead to a deterioration in air quality.
With the sudden spike in pollution levels a day after Diwali, “Most areas went from moderate to poor air quality”, says Chatterjee.
The air quality index (AQI) in several parts of the national capital worsened and remained high post Diwali as well.
If India were to experience a colder-than-usual winter, the AQI will worsen than what it already is as temperatures drop, atmospheric movement slows.
He explains that during winters, the winds are calm (or at low speed), and the earth warming is significantly less, because of less radiation from the sun reaching the surface, due to which the air near the surface is less heated.
The vertical lift of the air is inhibited due to this. So, as pollutants produced near the surface of the earth cannot rise up, “there is restricted vertical dispersion”, and thus these pollutants get accumulated closer to the ground.
“The boundary layer is the portion of the atmosphere closest to the earth’s surface where pollutants accumulate. Once the boundary layer decreases, it enhances the level of pollution to a large extent.”
Abhijeet ChatterjeeIn other words, with pollutants experiencing “high atmospheric stability”, there's less scope of escape, and more of accumulating near the surface.
Chatterjee further says that the burning of firecrackers during a transition period (when the winter just sets in) promotes and accelerates further pollution.
The residual effect due to Diwali gets added up to the normal winter pollution activities. All of this together, helps pollution levels sustain as the country witnesses a further surge.
“Cities such as Delhi and Kolkata are likely to witness severe pollution episodes, especially as Diwali-related emissions could catalyse the situation this year.”
Expand3. Colder Winters, Higher Health Risks
With severe winter season, and intensified pollution, experts warn that the health impact will be more severe, too.
According to the recently released The Lancet Countdown on Health and Climate Change report, exposure to PM2.5, an ultra-fine particulate pollutant which causes air pollution, was linked to over 1.7 million deaths in India in 2022, a 38 percent increase since 2010.
Dr Pritha Bhattacharjee, associate professor at the University of Calcutta and principal investigator of the Environmental Epigenomics Laboratory, tells The Quint that climatic shifts—from heavy rainfall to cold stress—can trigger a spike in common ailments like cough, fever, and respiratory infections, and, in severe cases, lead to pneumococcal infections, asthma, and bronchitis.
“In general, it's the older and the younger population who are more susceptible. But lifestyle disorders like sedentary patterns, ultra-processed food intake, and sleep pattern irregularity have been making young adults susceptible to health problems as well.”
Dr Pritha BhattacharjeeDr Bhattacharjee explains that during winter, thermal inversion traps pollutants, worsening air quality and aggravating respiratory problems. She adds that long-term exposure to changing climates can alter how genes function, affecting inflammation, immunity, and stress responses.
Repeated exposure to extreme weather, she notes, is especially harmful for lower socio-economic communities.
She explains that to avoid the cold, people often burn plastic, thermocol, wood, and other waste materials, which can gradually harm their lungs.
"For unusually cold winters, humanitarian support should be extended to vulnerable populations exposed to harsh conditions. The government and NGOs should work together to build shelter homes and ensure that basic necessities are available."
K VenkatramanaExpand
What’s Driving India’s Harsh Winter Ahead?
K Venkatramana, fellow at The Energy and Resources Institute (TERI), explains to The Quint that the IMD's projections of a colder winter are based on a mix of factors, which together allow cold air to linger over India longer than usual.
The influence of La Niña
Jet stream shifts
Regional ocean warming
La Niña is a climate event where cooler waters in the Pacific Ocean alter global wind and weather patterns.
"During this episode, India often experiences more frequent and longer cold waves."K Venkatramana
India has already witnessed the consequences of La Niña this year. In early October, north and northwest India saw sporadic showers, which lowered temperatures in the plains.
The Himalayas also received an early snowfall, along with isolated hailstorms in Jammu, western Rajasthan, and western Uttar Pradesh in early October.
Vishal Dixit, climate scientist and assistant professor at the Centre for Climate Studies, IIT Bombay, tells The Quint that the reason for these sporadic showers and early snowfall in the Himalayas is a consequence of the storm tracks over the Mediterranean and the western Himalayas becoming active due to the shift in jet streams caused by La Niña.
Furthermore, the warming of the Arabian Sea along with these changes prolong the cold wave conditions over north India.
According to the US-based NOAA Research, a research and development body to enable better forecasts, earlier warnings for natural disasters, and a greater understanding of the earth, a cycle of warm El Niño and cool La Niña episodes that happen every few years in the tropical Pacific Ocean is "the most dramatic year-to-year variation of the earth’s climate system, affecting agriculture, public health, freshwater availability, power generation, and economic activity" around the global.
Colder Winters Likely to Worsen Air Pollution Across India
As India prepares for a colder winter, Professor Abhijeet Chatterjee of Bose University, Kolkata, warns that this could further lead to a deterioration in air quality.
With the sudden spike in pollution levels a day after Diwali, “Most areas went from moderate to poor air quality”, says Chatterjee.
The air quality index (AQI) in several parts of the national capital worsened and remained high post Diwali as well.
If India were to experience a colder-than-usual winter, the AQI will worsen than what it already is as temperatures drop, atmospheric movement slows.
He explains that during winters, the winds are calm (or at low speed), and the earth warming is significantly less, because of less radiation from the sun reaching the surface, due to which the air near the surface is less heated.
The vertical lift of the air is inhibited due to this. So, as pollutants produced near the surface of the earth cannot rise up, “there is restricted vertical dispersion”, and thus these pollutants get accumulated closer to the ground.
“The boundary layer is the portion of the atmosphere closest to the earth’s surface where pollutants accumulate. Once the boundary layer decreases, it enhances the level of pollution to a large extent.”Abhijeet Chatterjee
In other words, with pollutants experiencing “high atmospheric stability”, there's less scope of escape, and more of accumulating near the surface.
Chatterjee further says that the burning of firecrackers during a transition period (when the winter just sets in) promotes and accelerates further pollution.
The residual effect due to Diwali gets added up to the normal winter pollution activities. All of this together, helps pollution levels sustain as the country witnesses a further surge.
“Cities such as Delhi and Kolkata are likely to witness severe pollution episodes, especially as Diwali-related emissions could catalyse the situation this year.”
Colder Winters, Higher Health Risks
With severe winter season, and intensified pollution, experts warn that the health impact will be more severe, too.
According to the recently released The Lancet Countdown on Health and Climate Change report, exposure to PM2.5, an ultra-fine particulate pollutant which causes air pollution, was linked to over 1.7 million deaths in India in 2022, a 38 percent increase since 2010.
Dr Pritha Bhattacharjee, associate professor at the University of Calcutta and principal investigator of the Environmental Epigenomics Laboratory, tells The Quint that climatic shifts—from heavy rainfall to cold stress—can trigger a spike in common ailments like cough, fever, and respiratory infections, and, in severe cases, lead to pneumococcal infections, asthma, and bronchitis.
“In general, it's the older and the younger population who are more susceptible. But lifestyle disorders like sedentary patterns, ultra-processed food intake, and sleep pattern irregularity have been making young adults susceptible to health problems as well.”Dr Pritha Bhattacharjee
Dr Bhattacharjee explains that during winter, thermal inversion traps pollutants, worsening air quality and aggravating respiratory problems. She adds that long-term exposure to changing climates can alter how genes function, affecting inflammation, immunity, and stress responses.
Repeated exposure to extreme weather, she notes, is especially harmful for lower socio-economic communities.
She explains that to avoid the cold, people often burn plastic, thermocol, wood, and other waste materials, which can gradually harm their lungs.
"For unusually cold winters, humanitarian support should be extended to vulnerable populations exposed to harsh conditions. The government and NGOs should work together to build shelter homes and ensure that basic necessities are available."K Venkatramana