More than 1,300 excess deaths have been recorded across Europe since June 21 linked to high temperatures, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus said on social media platform X on Sunday.

"Right now 150 million people are living under extreme heat, hundreds have died, schools are shut, grids are buckling," Tedros said on X.

He warned that "heat stress is often called the 'silent killer' - and European homes, workplaces and schools were not built for these temperatures".

Europe is the fastest-warming continent on Earth, heating at twice the global average, Tedros noted. "Driven by climate change and global warming, the phenomenon of the 'once-in-a-generation' heatwave is now occurring" nearly annually, he said.

The WHO is working with its members and partners to address the health threats posed by extreme heat through focusing on preparedness, prevention and stronger health system responses. Tedros called on European countries to "implement heat health action plans" as part of the broader agenda to protect health against climate change.

Separately, the WHO has published practical tips for keeping cool during extreme heat on its website. The guidance recommends staying out of the heat by avoiding outdoor activity during the hottest time of day, staying in the shade, and spending two to three hours daily in a cool place.

To keep homes cool, the WHO advises using night air to cool down homes after dark, closing windows and covering them with blinds during the day when outdoor temperatures are higher than indoors, and turning off as many electrical devices as possible.

The guidance also warns that electric fans should only be used when temperatures are below 40 degrees Celsius -- in temperatures above 40 degrees Celsius, fans will heat the body. If using air conditioning, the WHO recommends setting the thermostat to 27 degrees Celsius and turning on an electric fan, which will make the room feel 4 degrees Celsius cooler and can save up to 70 percent on electricity bills for cooling.

To keep the body cool and hydrated, the WHO suggests wearing light and loose-fitting clothing, taking cool showers, wetting skin with a damp cloth or spray, and drinking water regularly -- at least one cup per hour and two to three liters per day.

The guidance also emphasizes checking in regularly with vulnerable people, especially those over 65 and those with heart, lung or kidney conditions, disabilities, or living alone.

The WHO also warns people never to leave children or animals in parked vehicles, to avoid direct sun exposure during peak hours, and never to cover an infant stroller with dry fabric -- which makes it hotter inside -- but instead use a wet, thin cloth and re-wet as necessary.