Why Delhi Is Heating Faster Amid India’s Heatwave Alerts

Delhi will see clear skies, with temperatures expected to touch around 40 degrees Celsius on April 20, according to the India Meteorological Department (IMD), which has issued a yellow alert for heatwave conditions later in the week.

While the national capital braces for rising heat, other parts of India may see rain and thunderstorms.

Reasons Behind Delhi’s Heat

According to reports, Delhi’s temperature is rising rapidly due to a combination of seasonal and local factors. Clear morning skies allow intense solar radiation to heat the surface quickly, while urban materials like concrete trap and amplify this heat.

As the sun’s angle increases in late March–April, this effect intensifies, pushing temperatures higher earlier in the day.

States Under Heatwave Alert

Heatwave conditions are expected over large parts of central and northern India. According to the India Meteorological Department (IMD), these states include Madhya Pradesh, Chhattisgarh and Vidarbha, along with Uttar Pradesh, Rajasthan, West Bengal, Jharkhand, Punjab, Haryana and Odisha. These regions are expected to experience sustained high temperatures over the next few days.

Southern states such as Kerala, Tamil Nadu, Puducherry, Andhra Pradesh and Karnataka are also likely to face hot and humid conditions, adding to overall discomfort.

The IMD has also warned of warm night conditions in Haryana, Chandigarh, Uttar Pradesh and Odisha. This means temperatures will remain elevated even after sunset, offering little relief from the daytime heat.

Heatwave Criteria in India

A heatwave is a time when temperatures are much higher than normal for a certain area. Because of this, the temperatures at which heatwaves are declared vary from place to place based on the historical temperatures of that area. Heatwaves are worse when there are other weather conditions that make them worse, like high humidity, high wind speed and long heatwave events.

For plains, a heatwave is considered when the temperature rises to 40 degrees Celsius or higher in flat areas and 30 degrees Celsius or higher in hilly areas. When temperatures are 4.5 to 6.4 degrees Celsius above normal, a heatwave is declared. When the difference is more than 6.4 degrees Celsius, a 'severe heatwave' is declared.

A heatwave is declared when the temperature reaches 45 degrees Celsius or higher, and a severe heatwave is declared when the temperature reaches 47 degrees Celsius or higher. According to IMD, the criteria must be met in at least two stations within a meteorological subdivision for two consecutive days, with the declaration made on the second day.

For coastal areas, slightly different rules apply: a heatwave may be declared when the temperature is at least 4.5 degrees Celsius above normal, provided the actual maximum reaches 37 degrees Celsius or more.

Urban Heat and Risks

According to the 2024 report published by Social and Policy Research Foundation, Delhi's urban heat islands result from intense concretisation and rapid green cover loss.

These hotspots make nighttime temperatures much higher and raise health risks like dehydration and heat stroke. Extreme heat also poses a threat to the economy, as it could cut outdoor workers' productivity by a significant 15% by 2050.

Staying Safe During Heatwaves

According to the Apollo website, staying safe during a heatwave requires a mix of hydration, diet, and limited exposure. Health advisories recommend drinking plenty of water and fluids like coconut water or buttermilk to prevent dehydration. Avoid stepping out during peak afternoon hours, wear loose cotton clothing and eat light, water-rich foods while avoiding caffeine, alcohol and heavy meals.

Keeping indoor spaces cool, taking frequent breaks, and recognising early symptoms like dizziness or fatigue are also critical to preventing heat-related illnesses.