Spanish rescuers took AFP through the warning signs and best responses to the potentially fatal condition, as a heatwave grips Spain, Portugal, France and the Balkans.
Scientists warn that periods of extreme heat will become longer, more frequent and more intense as human-induced climate change accelerates.
- Symptoms -
In a large room at Madrid's Isabel Zendal hospital, emergency medical staff adjusted their headphones and fixed their gaze on their computer screens.
They receive 3,500 calls every day, some caused by falls, fainting and other dangers linked to overheating.
But identifying heatstroke straight away is "difficult", said Gemma Rodriguez, a team leader at the SUMMA 112 emergency service.
The symptoms can "point to another condition, for example, an unconscious person, a person who has fallen over... or has trauma, and the primary cause could have been heatstroke", she told AFP.
To diagnose the condition, doctors typically examine whether the patient has a body temperature of over 40 degrees Celsius (104 degrees Fahrenheit); whether their skin is hot and dry; or whether they are sweating heavily, nauseous or vomiting, she added.
In extreme cases, heatstroke can cause incoherent speech and loss of consciousness, and can even prove fatal if left untreated.
Rodriguez said vulnerable groups like children, the elderly and people with chronic illnesses should pay particular attention to the warning signs.
She recalled the case of an elderly couple with Alzheimer's disease who spent several hours in the sun in the countryside in early June.
The man tumbled into a ditch and the woman fainted, but they are now out of danger thanks to the intervention of SUMMA 112, she told AFP.
- Treatment -
When someone has heatstroke, the priority is to bring down their body temperature, for example by moving them into the shade or an air-conditioned room -- anything to shield them from the sun, Rodriguez explained.
"Another method is to use compresses, cool them with serums, or (apply) water and ice" to the armpits, forehead, neck, genital area and stomach, she said.
"In the most extreme and serious cases", Rodriguez added, patients may need to be given therapeutic serums intravenously.
- Prevention -
To avoid heatstroke, people should avoid sun exposure during the hottest hours of the day, generally from midday to 4 pm, Rodriguez said.
The advice is particularly relevant to sports enthusiasts and people who work outdoors, like street sweepers and labourers, she added as she unfolded a survival blanket designed to keep patients cool.
It is also important to stay hydrated, wear light clothing and caps, and stay in the shade or air-conditioned spaces, Rodriguez told AFP.
For active types unable to resist a workout, she had a simple message: "avoid those (hot) hours or do it in an air-conditioned room".
Heatwave triggers health warnings across Balkans
Zagreb (AFP) June 26, 2025 -
Temperatures soared across the Balkans on Thursday, with parts of the region expected to hit 41 degrees Celsius (106 Fahrenheit), triggering heatwave health warnings.
In Croatia, the capital Zagreb and the country's east were at the highest risk of heat, according to the national Meteorological and Hydrological Service.
Authorities remained on high alert after forest fires over the weekend destroyed dozens of homes on the country's tourism-oriented southern coast.
Albania said its firefighters managed to control eight blazes in the past 24 hours.
Meteorologists in Bosnia warned people to stay indoors as parts of the country were predicted to climb to 41C.
"Be ready to suspend outdoor activities and prepared for high temperatures that will lead to health risks among vulnerable people, like the elderly and very young," Bosnia's meteorological institute said.
This is the first of at least three heatwaves expected during the June-August period in Bosnia, said Bakir Krajinovic from the country's Federal Hydro-Meteorological Institute.
Temperatures so far this month have already exceeded forecasts, and predictions for July and August indicate temperatures will be four to five degrees above average, Krajinovic said.
It was also the driest June on record in Bosnia, with the lowest rainfall since measurements began 135 years ago.
Krajinovic said climate change was driving "more intense" weather events and breaking records "more often".
Parts of Serbia are predicted to climb to 39C, also significantly above seasonal average, according to Serbia's National Hydrometeorological Service.
The heat is expected to ease by Friday, with temperatures slightly dropping over the weekend, before climbing again next week, according to weather forecasts for several Balkan nations.
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