The iconic Citgo sign’s distinctive red neon triangle near Fenway will go dark for one hour later this month, along with the cables of the Zakim Bridge, normally illuminated at night.

The two landmarks, along with dozens of other marquee Boston properties, such as the Prudential Center, Hancock Buildings and the Custom House Tower, will turn off all their nonessential lights from 8:30 p.m. to 9:30 p.m. on March 28, as Boston joins nearly 400 other cities worldwide in observing Earth Hour, Mayor Thomas M. Menino will announce today.

The event, organized by the World Wildlife Fund to raise awareness of climate change, is a continuation of last year’s Lights Out Boston campaign in which property owners were asked to kill their lights from 11 p.m. until dawn to reduce energy consumption.

Last year, 371 cities in 35 countries took part in Earth Hour, which saw Rome’s Colosseum, the Golden Gate Bridge, and the Empire State Building go dim for an hour, said City Councilor John Connolly, who pushed through a resolution last week endorsing the event.