As Delhi prepares to bid farewell to 2025, residents may have to contend with a foggy and heavily polluted New Year’s Eve, according to the latest forecasts from the India Meteorological Department (IMD) and other weather experts. Friday saw the city’s air quality index (AQI) jump sharply into the “very poor” category, accompanied by a thin layer of fog, signaling deteriorating environmental conditions as the winter season deepens.

The IMD has issued a yellow alert, the first level in its three-tier warning system, indicating the likelihood of dense fog over the weekend and into the early days of 2026. Dense fog is expected particularly on the mornings of Saturday and Sunday, affecting visibility and posing potential risks for road and air traffic. Senior officials and experts have cautioned that the weather is likely to remain unfavourable for the city’s residents as the year ends.

Air Quality Deteriorates

Friday’s pollution levels saw a significant jump after a brief period in the “poor” zone. By 4pm, the Central Pollution Control Board (CPCB) recorded Delhi’s AQI at 332, up from 271 on Wednesday and 234 on Thursday. By 10pm, the AQI rose further to 349, with 10 out of the city’s 40 monitoring stations entering the “severe” category. The increase has been attributed to slower winds, which prevent the dispersion of pollutants, and to atmospheric conditions that encourage the formation of fog.

Experts note that fog acts as a natural trap for pollutants, keeping particulate matter close to the ground and worsening air quality. This combination of dense fog and stagnant air has contributed to the current “very poor” AQI readings, raising concerns about respiratory health, particularly for vulnerable populations such as children, the elderly, and people with pre-existing conditions.

Role of Western Disturbances

A major factor influencing Delhi’s current and upcoming weather is the impact of western disturbances—weather systems that originate over the Mediterranean Sea, pass through Iran and Afghanistan, and reach northern India. As these systems encounter the Himalayan ranges, the moist air is forced upward, cooling rapidly and releasing precipitation in the form of snow in the mountains and rain or fog over the plains.

According to IMD scientists, the first western disturbance affecting the region has already led to a drop in wind speeds and an increase in humidity, conditions conducive to fog formation. Meteorologists warn that a second disturbance, expected from December 30 to January 1, could compound the problem, potentially bringing dense to very dense fog across the Indo-Gangetic Plains, including Delhi.

“Two consecutive western disturbances are now going to impact the region. While the impact of the first has already begun—leading to wind speeds dipping and moisture levels rising—the second is expected to strengthen the fog effect from December 30 onwards,” said Mahesh Palawat, Vice President at private weather forecaster Skymet.

Government and Expert Warnings

The state’s Environment Minister, Manjinder Singh Sirsa, has reiterated the IMD’s warnings, cautioning residents to be prepared for deteriorating conditions. “According to the Meteorological Department, there is a high possibility of dense fog. Based on data from previous years, Delhi’s weather is likely to worsen as we approach New Year’s Eve,” Sirsa said.

Despite these warnings, the Centre’s Early Warning System (EWS) for Delhi’s pollution predicts that the AQI is unlikely to reach the “severe” category again before the year ends. However, forecasters acknowledge that the system has been unreliable at times this winter, having failed to anticipate a sudden spike in pollution earlier in the week that led to AQI entering the “severe” zone on Tuesday. This highlights the challenges in predicting air quality, particularly during winter months when temperature inversions and calm winds can trap pollutants near the surface.

Temperature Trends

While pollution and fog dominate concerns, temperatures in Delhi are expected to remain near normal for this time of year. The minimum temperature on Friday was 7.7°C, hovering around the seasonal average. Forecasts suggest that minimum temperatures may remain between 5°C and 7°C until Sunday, before gradually rising to 7°C–9°C by New Year’s Eve.

Daytime temperatures, meanwhile, are expected to stay mild. Friday recorded a maximum of 22.3°C, roughly two degrees above normal, and similar temperatures are anticipated through December 29. On New Year’s Eve, temperatures may rise slightly to a range of 23°C–25°C, offering a relatively warm backdrop to the otherwise fog-laden and polluted cityscape.

Implications for Daily Life

The combination of dense fog and “very poor” air quality is expected to disrupt normal life in multiple ways. Reduced visibility could pose risks for motorists, pedestrians, and commuters, while lingering smog may exacerbate respiratory and cardiovascular health issues. Authorities have advised limited outdoor activity, the use of masks, and special care for vulnerable groups.

Air quality concerns are particularly pressing for New Year celebrations, which traditionally involve fireworks and outdoor gatherings, potentially aggravating already poor conditions. Experts have urged residents to exercise cautionand, if possible, avoid areas with heavy vehicular traffic during early morning hours when fog and pollution are at their peak.

Scientific Insights on Fog Formation

According to RK Jenamani, a senior scientist at IMD, wind speed plays a crucial role in fog intensity. Calm winds allow moisture to condense near the ground, thickening the fog layer. In Delhi, wind speeds are expected to remain low over the weekend, creating ideal conditions for fog accumulation. Combined with residual pollutants in the air, this could reduce visibility drastically, affecting transportation and daily activities.

Palawat added that previous western disturbances have shown similar patterns, where reduced wind speeds and increased humidity lead to widespread dense fog over the plains. With the second disturbance imminent, the region may witness persistent low visibility and smog, raising the AQI to “very poor” levels or higher, depending on local emission sources.

Looking Ahead

As Delhi approaches the end of 2025, weather experts emphasize that the fog and pollution are not short-lived phenomena. Residents should prepare for several consecutive days of low visibility and poor air quality, particularly during early mornings. Authorities may need to enhance monitoring, regulate traffic, and issue timely advisories to minimize health risks.

While western disturbances are not expected to cause a sharp drop in temperatures, the interplay of fog, humidity, and calm winds will likely dominate the city’s weather narrative over the coming days. The New Year’s celebrations, traditionally associated with outdoor gatherings and firework displays, may face constraints due to these conditions, potentially impacting public health and safety.

Conclusion

In summary, Delhi is likely to ring in 2026 under a dense shroud of fog and elevated pollution levels. The IMD’s yellow alert, coupled with predictions of dense fog due to consecutive western disturbances, points to a challenging weather scenario. With air quality already in the “very poor” zone and visibility expected to decrease further, residents are being urged to exercise caution, minimize outdoor exposure, and follow health advisories.

The combination of stagnant winds, increased moisture, and lingering pollutants underscores the complex interaction of meteorology and urban air quality in Delhi. While temperatures remain relatively mild, the twin challenges of fog and smog are likely to define the city’s weather narrative as the year ends, potentially impacting daily life, transportation, and New Year celebrations.