Millions of people across the world are preparing to turn off the lights Saturday night. Earth Hour is 8:30 to 9:30 p.m. local time.
Earth Hour has become a worldwide phenomenon. People turn off all unnecessary lights for just one hour as a way to help the planet.
The organizers say it's all about people uniting in a common goal.
Many cities in the valley are going to take part, including Phoenix. The lights at City Hall will be turned off as the city shows its support in protecting the environment.
The campaign is largely a symbolic one -- raising awareness of how much energy we all use on a daily basis and its impact on our resources.
Earth Hour started 7 years ago, and people in more than 150 countries are taking part.
By the way, lights that affect public safety are not part of the program -- only non-essential lights.