A Wet Bulb moment looms ...

A farmer pours water on himself while working at a wheat farm in the Ludhiana district of Punjab, India, on Sunday, May 1, 2022. Credit: T. Narayan/Bloomberg via Getty Images

It's May 4th ...

Cities across the region broke monthly April records. Temperatures have topped 100 degrees Fahrenheit across much of the region and have jumped above 110 F in many areas. New Delhi saw temperatures climb above 110 F for several days on end.

In parts of Pakistan, the heat rose even higher. Jacobabad exceeded 120 F on Saturday, likely the highest temperature recorded anywhere in the Northern Hemisphere last month. The city of Nawabshah topped it the next day with a staggering 121.1 F, according to climatologist Maximiliano Herrera, who tracks extreme temperatures around the world.

The city came close to beating its all-time record. On April 30, 2018, Nawabshah recorded a high temperature of 122.4 F — believed to be the highest reliably recorded April temperature ever observed in the Northern Hemisphere.

A web bulb moment looms. It's only a matter of time

A sling psychrometer. The sock is wet with distilled water and whirled around for 

a minute or more before taking the readings.

Wet bulb temperature is the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure. It is therefore measured by wrapping a wet wick around the bulb of a thermometer and the measured temperature corresponds to the wet bulb temperature. The dry bulb temperature is the ambient temperature. The difference between these two temperatures is a measure of the humidity of the air. The higher the difference in these temperatures, the lower is the humidity. 

In other words ...

The wet-bulb temperature (WBT) is the temperature read by a thermometer covered in water-soaked cloth (a wet-bulb thermometer) over which air is passed.[1] At 100% relative humidity, the wet-bulb temperature is equal to the air temperature (dry-bulb temperature); at lower humidity the wet-bulb temperature is lower than dry-bulb temperature because of evaporative cooling.

End result ...

Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (130 °F). The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is a wet-bulb temperature of 35 °C (95 °F) – theoretically equivalent to a heat index of 70 °C (160 °F), though the heat index does not go that high.[3]

Any questions?