It's hard to beat the sweltering heat in the Indian desert city of Sri Ganganagar, a reality that millions across the vast country will face with climate change in the coming decades.

While people in wealthy nations can find some relief from global warming with air conditioners and other modern luxuries, many here - and elsewhere in India - don't even have running water.

Sri Ganganagar, in the desert state of Rajasthan near the Pakistani border, is regularly the hottest place in India and temperatures of 50 degrees Celsius are nothing unusual.

So the region's two million residents - the equivalent of the population of Slovenia - wake up early during the long summer months.

By the late morning the sun is already sweltering and the temperature is sweltering at 42°C, everyone quickly retreats home until early evening.

Pointing to his large black umbrella, fruit seller Dinesh Kumar Shah said, "By noon, only those who cannot avoid it are outside. We just sit under that.”

Only a lucky few have air conditioners, as most people use fans, cheaper air coolers - between blackouts - and thick green curtains called tarpaulins to block out the sun.

"We the poor are the hardest hit," said Kuldeep Kaur, a local resident. Ceiling fans in our homes only distribute hot air.

“It is especially difficult for young children at home in the summer. But I think there's not much ordinary citizens can do about it. We just have to put up with it.”

Along the city's irrigation canals, young and old boys and men - but not the women of the socially conservative state of Rajasthan - cool off in the muddy waters.

The locals know the water drainage schedules. It helps them water their crops, and tells them where they should be to dive.

“This is better than any fan or air cooler,” said Arjun Sarsar, 16, who had already spent four hours chilling, literally, with his friends.

The average temperature in India rose by about 0.7 degrees Celsius between the start of the 20th century and 2018. It is set to rise another 4.4 degrees by 2100, according to a recent government report.

The study also predicts that the frequency of heat waves by then will be three to four times higher than it was in 1976-2005, and will continue to be twice as long.

According to a draft report from the United Nations' Advisory Committee on Climate Sciences, seen by AFP last month, hundreds of millions of people are likely to experience 30 days of deadly heat each year by 2080, even if the world meets the Paris climate agreement target. The limitation of warming to less than two degrees Celsius.

Constant heat waves can be very dangerous, especially when combined with high levels of humidity.

High humidity and heat together can create so-called "humid temperatures" to the point that sweating no longer cools people down, possibly killing a healthy adult within hours.

"Temperatures and humidity are increasing in India and all over the world," Roxy Matthew Cole, a climate scientist at the India Institute of Tropical Meteorology, told AFP.

"It's not only about heat waves but also the associated rise in humidity, which makes you feel that the temperature is much higher (than it is)," Cole added.

Indian cities are implementing "heat action plans,' planting trees in urban areas and painting roofs with reflective paint, but this is not a substitute for global action to reduce emissions.

Back in Sri Ganganagar, locals keep it cool by drinking plastic cups of sugarcane juice with mint leaves and lemon, and Mathura Choudhary sells them for 10 rupees ($0.13) each.

"This is the time when we are doing our best work," Chaudhry told AFP at his roadside booth. Who wouldn't love a glass or two of this in the summer? It's cool, sweet and refreshing.” Sitaram Sivta, filling the plastic water containers his company distributes to homes without running water, said city dwellers are accustomed to the summer heat.

"People live around it," he told AFP.

“It's not very hot. It's not the summer of Sri Ganganagar yet... (temperature) 41 or 42 only."