The Women's Euros begin in Switzerland today - with extreme heat warnings in place.
Security measures have had to be relaxed by UEFA for the opening matches so fans can bring in water bottles.
Temperatures could be about 30C (86F) when the Swiss hosts open their campaign against Norway in Basel this evening.
Players have already seen the impact of heatwaves this summer at the men's Club World Cup in the US.
It is raising new concerns in the global players' union about whether the stars of the sport are being protected in hot and humid conditions.
FIFPRO has asked FIFA to allow cooling breaks every 15 minutes rather than just in the 30th minute of each half.
There's also a request for half-time to be extended from 15 to 20 minutes to help lower the core temperature of players.
FIFPRO's medical director, Dr Vincent Gouttebarge, said: "There are some very challenging weather conditions that we anticipated a couple of weeks ago already, that was already communicated to FIFA.
"And I think the past few weeks were confirmation of all worries that the heat conditions will play a negative role for the performance and the health of the players."
Football has seemed focused on players and fans baking in the Middle East - but scorching summers in Europe and the US are becoming increasingly problematic for sport.
While climate change is a factor, the issue is not new and at the 1994 World Cup, players were steaming as temperatures rose in the US.
There is now more awareness of the need for mitigation measures among players and their international union.
FIFPRO feels football officials weren't responsive when it asked for kick-off times to be moved from the fierce afternoon heat in the US for the first 32-team Club World Cup.
FIFA has to balance the needs of fans and broadcasters with welfare, with no desire to load all the matches in the same evening time slots.
Electric storms have also seen six games stopped, including a two-hour pause during a Chelsea game at the weekend.
This is the dress rehearsal for the World Cup next summer, which is mostly in the US.
The use of more indoor, air conditioned stadiums should help.
There is no prospect of moving the World Cup to winter, as Qatar had to do in 2022.
And looking further ahead to this time in 2030, there will be World Cup matches in Spain, Portugal and Morocco. The temperatures this week have been hitting 40C (104F) in some host cities.
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FIFA said in a statement to Sky News: "Heat conditions are a serious topic that affect football globally.
"At the FCWC some significant and progressive measures are being taken to protect the players from the heat. For instance, cooling breaks were implemented in 31 out of 54 matches so far.
"Discussions on how to deal with heat conditions need to take place collectively and FIFA stands ready to facilitate this dialogue, including through the Task Force on Player Welfare, and to receive constructive input from all stakeholders on how to further enhance heat management.
"In all of this, the protection of players must be at the centre."
(c) Sky News 2025: Women's Euros: Extreme heat warnings in place as tournament kicks off