On Makar Sankranti, January 14, 2026, Delhi and the National Capital Region (NCR) experienced a sudden and intense "flash fog" phenomenon that dramatically reduced visibility to near zero within minutes, catching residents by surprise. The fog, which appeared between 7:45 and 8 am, dissipated almost as quickly as it formed, differentiating it from typical overnight radiation fog. Meteorologists have attributed this rapid-onset fog to a specific combination of atmospheric conditions prevalent in North India during winter. Key factors include ongoing cold wave conditions, high moisture levels in the atmosphere, and sudden shifts in wind and temperature. As the sun began to rise, instead of a gradual warming, a brief influx of colder air, likely due to light wind changes, caused ground-level temperatures to dip or stagnate abruptly. This rapid cooling pushed the air to its dew point, triggering immediate condensation of water vapor into dense fog. The exceptional density of this flash fog can be further explained by high humidity and the presence of pollution particles in urban areas like Delhi-NCR, which act as condensation nuclei, providing more surfaces for water vapor to cling to. Low wind speeds also played a crucial role, preventing the fog from dispersing and allowing it to pool rapidly across various areas. The quick dissipation of the fog was due to strengthening sunlight and increased air movement, which raised surface temperatures enough to break the delicate balance, causing water droplets to evaporate. This "flash fog" event caused significant disruptions, impacting transportation and posing safety risks as it offered little time for warnings. The India Meteorological Department (IMD) has issued warnings for persistent cold wave and dense fog conditions across North India, indicating that such rapid fog episodes might recur. The situation is exacerbated by already poor air quality in Delhi, with the Air Quality Index (AQI) frequently in the 'very poor' to 'severe' categories, a recurring winter challenge for the region. The long-term increase in frequency and intensity of fog in North India is also linked to land-use changes and rising pollution.