Delhi shivers at 3.8°C; flash fog grips capital — here’s why it happens | Today News

Delhi shivered through a morning of extreme cold on Wednesday, as the capital's temperature plummeted to a low of 3.8 degrees Celsius. Between 7:45 and 8:00 AM, a heavy, sudden blanket of mist swept across the landscape, reducing visibility to almost zero in moments, India Today reported.

This brief but powerful event is known as “flash fog” or rapid-onset fog, a phenomenon that develops and dissipates swiftly under specific weather conditions.

Weather experts attribute this to a combination of cold wave patterns, high humidity, and sudden changes in wind and temperature levels. The environment already held significant moisture left over from the previous night.

As dawn broke, rather than steady solar warming, a surge of chilled air caused by shifting light winds made surface temperatures stall or drop instantly. This fast cooling forced the air toward its dew point, sparking immediate condensation.

In high-moisture scenarios, even minor thermal fluctuations yield dramatic outcomes. In metropolitan hubs like Delhi-NCR, atmospheric pollutants serve as condensation nuclei, providing water vapour with extra surfaces to attach to. Consequently, according to the India Today report, visibility can collapse to just several meters within minutes.

Stagnant air also contributed. Lacking sufficient breeze to scatter the mist, the fog accumulated quickly over highways, neighbourhoods, and parks. Eventually, as the sun intensified, ground temperatures climbed enough to disrupt the fragile equilibrium. This warming, paired with a slight increase in air circulation, caused the droplets to revert into vapour, the report added.

The fog didn't drift elsewhere; it essentially vanished. Such abrupt events are hazardous, catching drivers and aviation professionals by surprise. Unlike predicted overnight conditions, flash fog provides no time for alerts, creating major safety hazards.

As the winter season deepens, forecasters suggest these rapid fog incidents may return, brief, intense, and chaotic, much like today’s unexpected occurrence.

Delhi's air quality continued to remain a serious concern on Wednesday morning, with the overall Air Quality Index (AQI) recorded at 357 at 7 am, falling in the 'very poor' category, according to data from the Central Pollution Control Board (CPCB). This marks a further deterioration compared to Tuesday, when the city's AQI stood at 337.

Several areas across the national capital reported AQI levels well above 300, indicating persistently hazardous conditions for public health. Anand Vihar recorded an AQI of 366 at 7 AM, while Bawana stood at 361. Jahangirpuri witnessed particularly alarming levels, with the AQI touching 420, placing it in the 'severe' category. RK Puram recorded an AQI of 407, Dwarka Sector 8 at 403, Punjabi Bagh at 366, Wazirpur at 386, and Chandni Chowk at 397, according to CPCB data.