"Earth Hour" is Saturday night, and Minneapolis and St. Paul are two of the 7,000 cities globally that will cut the lights in observance of the climate change and energy saving initiative.
All cities participating in Earth Hour will do so from 8:30 to 9:30 p.m. in their respective time zones.
City officials in Minneapolis and St. Paul said they will turn off "all uses of electricity in municipal buildings that is not required for life, safety or operations" during that time period, Minnesota Public Radio reports.
Minneapolis has participated in Earth Hour since 2008.
The City of St. Paul says among the building going dim are the Minnesota Capitol, City Hall and Ramsey County Courthouse, Landmark Center, Xcel Energy Center, RiverCentre, Rice Park, Saint Paul Central Library, Wells Fargo Place and First National Bank.
Earth Hour started in 2007 in Sydney, Australia.
Since then, it has grown from a national observance there to an international one, with more than 150 nations now participating. It bills itself as the "largest symbolic mass participation event in the world."