India has hottest day on record as temperature hits 51C

On Wednesday, India had its hottest day on record, with the temperature soaring to a scorching 51C (123.8F) in the city of Phalodi in Rajasthan.

The state of Rajasthan borders with Pakistan and consists largely of desert landscape, so it is no stranger to intense heat.

But even for a place used to high temperatures, to surpass 50C is pretty impressive and beats the old record of 50.6C that was set in 1956.

Heatwaves are an annual occurrence in India prior to the arrival of the seasonal south west monsoon rains. But this year’s heatwave has been particularly intense – killing more than 300 people so far this year.

During recent days, the most intense heat has been observed in the north west of India, with Rajasthan along with Jammu and Kashmir having maximum temperatures at least 5C above normal.

This might not sound like a lot, but when typical maximum temperatures are 40-45C, anything above normal increases the danger to life.

Why so hot?

Each year as summer approaches, the increasingly strong sun heats up the Indian continent, causing temperatures to soar.

As the days become longer than the nights, there are a greater number of hours where heating of the land is taking place than night time cooling.

This allows the heat to build and build ahead of the south west monsoon rains that start to arrive late May or early June.

It is thought that the occurrence of the recent El Nino has enhanced the strength of this year’s heatwave, by making drought more severe.

Latent heat

When the land is extremely dry, all of the sun’s energy goes into heating the ground and in turn the air just above it – boosting the potential to get higher than normal temperatures.

If there is moisture present in the ground, some of the sun’s energy will be used up evaporating this, taking some of the energy away from heating the ground and therefore lessening the potential to get higher than normal temperatures.

This process of energy being used to evaporate moisture is known as latent heat transfer and even though you can’t see it, you can test it for yourself.

If you blow on the back of your hand, it feels a little cooler than it did before you blew on it.

However, if you now put some room temperature water on the back of your hand and blow on it again, it will feel colder than it did the first time you blew on it.

This is because blowing on the water causes it to evaporate and use the latent heat on the surface of your skin, causing it to cool down.

Less hot in coming days

The latest forecast from the Indian Meteorological Department says that the heatwave will ease in the coming days, as temperatures tail off.

However, the only real relief from the heatwave will come when the south west monsoon rains arrive.

According to the Indian Meteorological Department, this year’s monsoon rains will arrive a week later than normal across Kerala, meaning that until then the heat will remain.

I’ll be keeping an eye on the heat and monsoon rains across Indian and posting updates on Twitter – @liamdutton

Images: earth.nullschool.net, Google, Indian Meteorological Department