On August 10, 2003, the United Kingdom records its first-ever temperature over 100 degrees Fahrenheit. Throughout the month, an intense heat wave scorched the European continent, claiming more than 35,000 lives.

August 2003 was the hottest August ever recorded in the northern hemisphere and broke all previous records for heat-related deaths. France was the worst hit, with almost 15,000 victims, followed by Germany, where approximately 7,000 people died. Thousands also died in Spain and Italy. A majority of the victims were elderly, very young, or chronically ill.

When a person experiences extreme heat, their bodies can struggle to cool themselves—which can prove especially dangerous in the very old, very young or already ill. If a person’s internal body temperature reaches 104 degrees Fahrenheit, the organs can began to fail and the person can eventually die. The Washington, D.C.-based Earth Policy Institute estimates that more people die every year from heat than floods, tornadoes and hurricanes combined.

In addition to directly causing deaths, the extreme heat also caused massive fires. In Portugal, 10 percent of the country’s forests were destroyed and 18 people were killed in the fires. The heat also caused glacial melt, flash floods and avalanches in Switzerland.

Scientists project that, because of global warming, the earth’s average temperature will continue to rise, reaching 42.44 degrees Fahrenheit by the end of the century, a gain of 2.5 degrees. Because of this, the World Meteorological Organization predicts that the number of annual heat-related deaths might double by 2023. Most researchers agree that the only way to stop the slow rise in global temperatures is to reduce levels of the carbon-dioxide emissions that contribute to global warming.

READ MORE: When Global Warming Was Revealed by a Zig-Zagged Curve