In the summer of 2003, Europe was very hot. Temperatures hit record highs in five countries.
In Paris, workers at the Eiffel Tower sprayed mist on hot tourists. The London Zoo cooled off its lions using ice. It was Europe’s hottest summer in 500 years. It caused at least 35,000 deaths.
That heat wave was a natural disaster. It was the deadliest one in the world that year. You can’t take great photos of hot weather. That’s one reason many people don’t take heat seriously. Every year, heat kills more Americans than hurricanes, tornadoes, floods, and lightning combined.

◀ Temperatures in the western U.S. are rising. This has led to drier forests. That has caused more forest fires over the last 30 years. Computer models say this warming could raise the number of forest fires by more than half.

Along with air and water, heat is a key part of Earth’s weather. Weather is the condition of atmospheric air. This is the air that surrounds Earth. Invisible gases like nitrogen, oxygen, and carbon dioxide make up 98 percent of it. The rest is other gases.

Humidity is a measure of water vapor in atmospheric air. High heat plus high humidity equals misery. Sweat won’t dry in high humidity, so it’s harder to cool off. In July 1995, temperatures in Chicago soared to 106°F, while the humidity rose, too. About 750 people died in that heat. ▶
◀ Temperatures in Paris reached 104°F on August 5, 2003. People cooled down under jets of water at Paris Beach. That’s a temporary beach on the banks of the Seine River.

Heat waves can cause serious health problems.

Try This!
Snowy tree crickets chirp faster on hot days. You can use their chirping to roughly compute the temperature. Count the number of chirps made in 13 seconds by one cricket. Now add 40 to that number. Then check a thermometer. How close were you?
Check It Out!
What’s the difference between weather and climate?
Weather is the day-to-day state of an area’s atmospheric air. Climate refers to average weather over a long period of time.