Heat Waves

Part of the Climate Change exhibition.

People cooling off at the Trocadero fountain in Paris, France during August 2003.
Franck Prevel/AP

While a single hot afternoon may be uncomfortable, it's hardly reason for panic. But when heat persists for days to weeks—a heat wave—crops wilt, roads buckle, animals suffer, and human death rates climb. Since 1950, long-lasting heat waves have struck much of the world more and more frequently, in places from the American Midwest to Europe. As average air temperatures continue to rise, heat waves will very likely become even more common.

What Makes Heat Waves So Dangerous?

Heat waves are marked by extreme daytime temperatures that can cause people to overheat and dehydrate. But what makes these events especially dangerous are high nighttime temperatures, which keep people from cooling down, resting, and rehydrating. The elderly are often at particular risk due to preexisting medical conditions and lack of mobility.

A woman tries to cool off during a weeklong heat wave in downtown Milan, Italy, 2005.
Luca Bruno/AP
2003 European Heat Wave: Things To Come?

Scientists can't say that a single weather event, such as the devastating 2003 heat wave in Europe, was caused by climate change. But that event was extremely unusual, and experts do predict that heat waves like the one in 2003 will be more common as Earth warms.

The summer of 2003 in southern and central Europe was 4°C (7°F) hotter than normal, probably the warmest in at least 500 years.

Temperatures in London, England, climbed above 38°C (100°F ) for the first time in 300 years. Temperature records were also broken in France, Germany, Switzerland, Spain, Italy, and Portugal.

Most European cities, including Paris, lack air conditioning and are ill-equipped to deal with such high temperatures.

Around 35,000 people died across Europe as a result of the high temperatures. It is estimated that in France alone, the heat wave claimed the lives of 15,000 people in August, about 10,000 of whom were over the age of 75.

The combination of extreme heat and little rain caused more than 13 billion Euros (over $14 billion at 2003 exchange rates) in ruined crops and other agricultural damages.

The water levels in major rivers such as the Loire were at record lows, disrupting inland navigation, irrigation, transportation, and industry.