Delhi Chokes as Dense Fog and Low Winds Push Air Quality to Severe Levels

​The capital city of Delhi is once again in the middle of a massive environmental and logistical crisis. Over the last few days, a thick, suffocating layer of smog has settled over the city, making it difficult for millions of people to breathe and even harder for them to travel. As of late December 2025, the Air Quality Index has officially hit the "severe" mark in many parts of the city, crossing the dangerous 400-point threshold. This toxic air is not just a health hazard; it has brought the city's transport systems to a grinding halt, with over 150 flights delayed and several others cancelled at the Indira Gandhi International Airport.

​The situation is a perfect storm of bad weather and heavy pollution. The combination of falling temperatures, very low wind speeds, and dense fog has created a "trap" for pollutants. Instead of blowing away, the smoke and dust are hanging low over the streets, turning the city into what many residents describe as a giant gas chamber. For those living in the National Capital Region, this is a grim reminder that despite various government measures, the winter air remains a significant threat to life and normalcy.

​The Science Behind the Smog Trap

​To understand why the air has become so bad so quickly, we have to look at the local weather conditions. Ordinarily, wind helps to carry away the pollutants generated by cars, factories, and construction sites. However, over the past 48 hours, wind speeds in Delhi have dropped significantly. When the air is calm, there is nothing to push the pollution out of the city.

​Adding to this is a phenomenon known as "temperature inversion." During winter nights, the ground cools down very fast. This cold air gets trapped under a layer of warmer air above it. Since cold air is heavier, it stays near the ground, acting like a lid on a pot. All the smoke from vehicles and biomass burning gets stuck under this lid. When you add high humidity and fog into the mix, these tiny water droplets grab onto the pollution particles, creating a thick, grey soup known as smog. This is why visibility has dropped to nearly zero in some parts of North India.

​Travel Chaos at Delhi Airport

​The most visible impact of this dense fog has been at the Delhi airport. As one of the busiest aviation hubs in the world, any disruption here has a massive ripple effect across the country. On Monday morning, visibility at the airport fell to as low as 50 to 100 meters. While modern aircraft are equipped with advanced landing systems like CAT III, they still require a minimum level of visibility to operate safely.

​Over 150 flights were delayed because the pilots simply could not see the runway clearly enough to taxi or take off safely. Passengers were left stranded for hours inside terminals, with many complaining about a lack of information from airlines. It wasn't just domestic flights that were affected; international schedules were also pushed back, causing a backlog that will take days to clear. The airport authorities issued several advisories asking travelers to check their flight status before leaving home, but for many who were already at the gate, it was a long and frustrating wait.

​Severe Air Quality and Health Alarms

​While the flight delays are a massive inconvenience, the real danger lies in the air itself. The Central Pollution Control Board reported that the average AQI for Delhi hit 402 this week. In specific hotspots like Anand Vihar, Vivek Vihar, and Jahangirpuri, the numbers were even higher, sometimes crossing 450. At these levels, the air is considered hazardous even for healthy adults, let alone children or the elderly.

​Doctors in the city are reporting a sharp increase in patients coming in with respiratory issues, stinging eyes, and persistent coughs. The fine particulate matter, known as PM 2.5, is so small that it can enter the bloodstream and damage vital organs. The government has already triggered the Graded Response Action Plan (GRAP) Stage IV, which is the highest level of emergency measures. This includes a ban on most construction activities and restrictions on the entry of heavy trucks into the city. However, many experts believe these are reactive measures that do little to solve the root cause of the problem.

​The Impact on Trains and Road Traffic

​The crisis isn't limited to the skies. The Indian Railways also reported that dozens of trains arriving in and departing from Delhi were delayed by several hours. In some cases, trains were running six to eight hours behind schedule because drivers had to slow down to a crawl to avoid accidents in the zero-visibility conditions.

​On the roads, the situation was equally dangerous. Major highways like the Delhi-Meerut Expressway and the Western Peripheral Expressway saw multiple vehicle pile-ups due to the fog. The police have been urging drivers to use fog lights and keep a safe distance from other vehicles, but the combination of poor visibility and toxic air makes every commute a risk. The smog is so dense that even during the day, streetlights in some areas remain on because the sun cannot penetrate the layer of pollution.

​Why Does This Keep Happening?

​Every year, the same story unfolds in Delhi, and every year, people ask why. While weather is a major factor, human activity provides the fuel for the fire. Vehicular emissions remain the largest contributor to Delhi's local pollution, accounting for nearly 20% of the load. Industrial smoke, dust from unpaved roads, and the burning of waste also play a part.

​In late December, the impact of stubble burning from neighboring states is usually lower than in October or November, but the "residual" pollution remains. Because the air is so heavy and still, the pollution produced within the city today stays in the city tomorrow. We are essentially breathing our own exhaust. Until there is a massive shift toward electric vehicles, better public transport, and a complete halt to open waste burning, the capital will continue to face these "severe" days every winter.

​What Can Citizens Do?

​In the face of such a massive environmental failure, individuals are often left to fend for themselves. Health experts recommend staying indoors as much as possible, especially during the early morning and late evening when pollution levels are at their peak. For those who must go out, N95 masks are the only effective barrier against the tiny PM 2.5 particles.

​Inside homes, air purifiers have become a necessity rather than a luxury for many families. However, these are expensive and out of reach for the majority of the population. This highlights the social inequality of air pollution: the people who contribute the least to the problem, such as outdoor laborers and those living in slums, are often the ones most exposed to the toxic air without any protection.

​Looking Ahead to the New Year

​The weather department has warned that these conditions are likely to persist for at least another few days. A "Western Disturbance" is expected to bring some change in wind patterns by the first week of January, which might provide a temporary reprieve. However, until that happens, the city remains under an "Orange Alert" for dense fog and severe air quality.

​The recurring nature of this crisis suggests that the current "emergency" approach is not working. We need a year-round strategy that focuses on reducing emissions at the source rather than just banning construction once the air is already unbreathable. For now, the people of Delhi can only wait for the wind to pick up and the fog to clear, hoping for a breath of fresh air in the new year.