No rain, only heat: Why Delhi feels like a furnace just before the monsoon

Delhi posted its hottest morning in nearly two years as monsoon moisture built over the city. The rising humidity pushed the feels-like temperature far above the actual reading ahead of the rains.

In Short

• Delhi logged a 31.1°C minimum, among its warmest June mornings
• Safdarjung recorded 41.8°C, while the heat index surged to 50.7°C
• Moisture from Arabian Sea and Bay of Bengal sharply raised humidity

Delhi woke up to its hottest morning in nearly two years on Sunday, with the minimum temperature refusing to drop below 31 degrees Celsius as the southwest monsoon continued to remain just out of reach.

The India Meteorological Department (IMD) recorded a minimum temperature of 31.1°C, nearly 3.2 degrees above normal, while the maximum climbed to 41.8°C at Safdarjung, 4.6 degrees above the seasonal average. At 5.30 pm, the weather office said the heat index, or "feels-like" temperature, touched a scorching 50.7°C.

The uncomfortable weather has left many wondering: if the monsoon is almost here, why does it suddenly feel hotter than before?

The answer lies in the atmosphere preparing for the arrival of the rains.

As the southwest monsoon advances northward, it transports enormous amounts of moisture from the Arabian Sea and the Bay of Bengal into northern India. Even before the first raindrops fall, this moisture begins accumulating in the lower atmosphere over Delhi-NCR. The result is a sharp rise in humidity, turning the air heavy and sticky.

Humidity changes the way the human body cools itself. Under normal dry conditions, sweat evaporates quickly from the skin, carrying away heat. But when the air is already saturated with moisture, evaporation slows dramatically.

Sweat remains on the skin instead of cooling the body, making temperatures feel several degrees higher than what thermometers record.

This is why meteorologists often refer to the "heat index" or apparent temperature. While Delhi's actual air temperature was around 42°C, the combination of heat and humidity made it feel closer to 51°C.

Weather experts describe this phase as pre-monsoon sultriness," a common feature before the onset of the monsoon across north India. It is often marked by oppressive humidity, warm nights and daytime temperatures that remain elevated because abundant moisture also traps heat near the surface.

Another reason nights have become unusually warm is the blanket-like effect of water vapour. Moist air absorbs and re-emits heat radiated from the Earth's surface after sunset, preventing temperatures from falling significantly overnight.

This explains why Delhi recorded one of its warmest June mornings in recent years.

The delay in the monsoon's arrival has only prolonged this uncomfortable spell.

Normally, once widespread monsoon rains begin, thick cloud cover blocks some incoming solar radiation while rainfall cools the land through evaporation and the influx of cooler air.

Until that transition happens, the city remains caught in an uncomfortable middle ground, moisture has already arrived, but the cooling rains have not.

The IMD has indicated that conditions are becoming favourable for the southwest monsoon to advance into Delhi-NCR in the coming days. When it does, temperatures are expected to fall noticeably.

Ironically, the unbearable heat and humidity gripping the capital may be one of the clearest signs that the monsoon is finally on its doorstep.

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