Delhi to touch 40°C: When does IMD issue heatwave alert?
What's the story
The India Meteorological Department (IMD) has issued a heatwave alert for several parts of north and central India, including Delhi. Temperatures in Delhi and Uttar Pradesh are likely to cross the 40°C mark in the coming days, indicating a quick transition into peak summer conditions. The IMD forecasts a 2-4°C rise above normal across northwest India, with states like Rajasthan, Madhya Pradesh, and Haryana also likely to see severe daytime heating.
Weather warning
Night temperatures may not drop below 30°C
The IMD has issued a yellow alert for Delhi, indicating increasing heat stress and the need for caution. One major concern is the emergence of warm night conditions, where temperatures remain unusually high even after sunset. This prevents the body from cooling down and increases the risk of heat exhaustion and dehydration, especially among vulnerable populations.
Weather patterns
Dry air and persistent high-pressure systems causing heatwave
The IMD attributes the heatwave to persistent high-pressure systems, clear skies, and dry air masses. These conditions trap daytime heat on land and prevent it from escaping at night. This creates a conducive environment for prolonged and intensifying heat waves. Meanwhile, other parts of India are witnessing contrasting weather patterns, with eastern and northeastern regions likely to see rain, thunderstorms, and gusty winds.
Temperature threshold
What constitutes a heatwave?
The IMD clarifies that a heatwave is not defined by temperature alone but by how unusual that temperature is for a region. In the plains of Delhi and Uttar Pradesh, 40°C is just the starting threshold. A heatwave is officially declared if temperatures are 4.5°C or more above normal or if they exceed 45°C, irrespective of averages.