Earth Hour is a campaign. It happens on the last Saturday of March. It tells people about climate change. It tells people to turn off the lights for one hour. Some people do so.
Earth Hour started in Sydney. It started in 2007. Now, around 7,000 cities turn off the lights. They save energy like this. They help the planet.
Difficult words: earth (our planet), campaign (a plan to tell people about something), climate change (the changing of the climate – weather).
