A new report backed by climate scientists and athletes warned Tuesday about the dangers posed by extreme high temperatures at this year's Paris Olympics.

The "Rings of Fire" report -- a collaboration between non-profit Climate Central, academics at Britain's University of Portsmouth and 11 Olympians -- said conditions in Paris could be worse than the last Games in Tokyo in 2021.

It warned that "intense heat at the Paris Olympics in July-August 2024 could lead to competitors collapsing and in worst case scenarios dying during the Games."

The study adds to a growing number of calls from sports people to adjust schedules and the timing of events to take into account the physical strain of competing in higher temperatures caused by global warming.

"Rings of Fire" urges organisers of competitions typically held at the height of the northern hemisphere summer -- such as the Olympics or the football World Cup -- to re-think their scheduling.

They should also provide improved rehydration and cooling plans for athletes and fans to avoid the risk of heat stroke, the study argued.

The Paris Olympics, which run from July 26-August 11, are set to take place in what are usually the warmest months in the French capital which has been struck by a series of record heatwaves in recent years.

More than 5,000 people died in France as a result of searing summer heat last year when new local highs above 40 degrees Centigrade (104 Fahrenheit) were recorded around the country, according to public health data.

A study in the Lancet Planet Health journal last May found that Paris had the highest heat-related death rates of 854 European towns and cities, partly due to its lack of green space and dense population.

Rainy conditions

Rather than high temperatures, incessant rain is currently the bigger weather-related concern for Paris 2024 organisers, with regular downpours in May and June leading to unusually strong currents in the river Seine and poor water quality.

The Seine is set to host a boat parade during the unprecedented opening ceremony being planned for July 26, as well as the triathlon swimming and marathon swimming events -- pollution permitting.

Organisers of Paris 2024 say they have built flexibility into their schedules, enabling them to shift around some events such as the marathon or triathlon to avoid the peaks of midday heat.

But much of the Games is set to take place in temporary stands that lack shade, while the athletes' village has been built without air conditioning to reduce the Games' carbon footprint.

"Sleep disruption due to heat has been cited in the build-up to the 2024 Games as a major concern by athletes, especially given the lack of air conditioning in the Olympic Village," the report said.

Olympic teams have been offered the possibility of installing portable air-conditioning units in their accommodation, however, which many have opted to include.

'New norm'

One of the athletes who backed the "Rings of Fire" report, Indian triathlete Pragnya Mohan, said she had left her home country because of high temperatures, with India recently reporting its longest ever heatwave.

"With climate change, the kind of heat that we experience has increased so much," Mohan told reporters. "I am not able to train in my country. That is one of the reasons that I moved to the UK."

Other athletes behind the report explained how athletes have adjusted their training to take into account global warming, either waking before dawn to preserve themselves or exercising in high-tech heat chambers to acclimatise to summer temperatures.

"I've found myself in conditions where you're literally trying to get through the next phase of play," Jamie Farndale, a rugby Sevens player for Britain, told reporters.

"I've had teamates who had heatstroke and have spent several days back in the hotel," he added.

The last Summer Olympics in Tokyo were widely thought to have been the hottest on record, with temperatures regularly above 30C coupled with 80 percent humidity.

Tokyo organisers moved the race walk events and two marathons 800 kilometres (500 miles) north of Tokyo in the hope of cooler weather that did not really materialise.

Despite a range of anti-heat measures including misting stations, many athletes struggled while performing, including Russian tennis player Daniil Medvedev who wondered aloud on court if he might die.

Speaking after Tokyo, World Athletics president Sebastian Coe, who wrote a foreword for "Rings of Fire", warned that the "new norm" was competing in "really harsh climatic conditions".