At least 16 people have died of heatstroke in southern India so far this summer, officials said on Sunday, as a heatwave grips swathes of the country following official health warnings.

India is no stranger to scorching summers but years of scientific research have found climate change is causing heatwaves to become longer, more frequent and more intense.

Temperatures in several cities across the country of 1.4 billion people have recently hovered well above 45 degrees Celsius.

The deaths were reported in the southern state of Telangana, with revenue minister Ponguleti Srinivasa Reddy calling for “statewide vigilance” to safeguard public health.

“The intensity of the heat has reached unprecedented levels” and officials in Telangana should issue advance warnings about precautions to be taken during heatwaves, Reddy’s office said in a statement.

Health experts say that extreme heat can lead to dehydration that thickens the blood and, in particularly severe cases, causes organs to shut down.

The local government in Telangana advised the elderly, children and pregnant women not to venture out in daytime unless necessary.

Earlier this week, the India Meteorological Department predicted above-normal temperatures and intense heatwave conditions in several parts of the country.

Temperatures in the capital New Delhi and other nearby cities have stayed over 40°C throughout this week, sending power usage soaring to record levels.

In addition to the burning midday heat, overnight minimum temperatures are also high, giving people little respite.

India, the world’s most populous nation, is the third-biggest emitter of greenhouse gases and relies heavily on burning coal for power generation.

It has committed to achieving a net-zero emissions economy by 2070 — two decades after most of the industrialised West.

The country’s highest officially recorded temperature is 51°C, measured at Phalodi in Rajasthan in 2016.