Why does it feel like 51°C in Delhi when the actual maximum temperature is 41.3°C?

The reason it feels like 51°C in Delhi even though actual maximum temperature is 41.3°C is because of a weather measurement called wet-bulb temperature. It measures combined effect of heat and humidity. When humidity is high, sweat doesn't evaporate easily from skin, making it harder for body to cool itself. Hence, people feel much hotter than actual air temperature.