If you're around downtown at 10 p.m. tonight, expect to see a sudden change.
Tonight begins the annual Lights Out Houston campaign, where businesses douse their nonessential lights during non-business hours, from 10 p.m. to 6 a.m.
Last year almost 90 million square feet of needlessly lit office space went dark, and there are pledges so far this year -- the event's fourth -- of more than 150 million square feet, organizers say.
Check out the web page if you have a business that would like to participate, or just, you know, turn the lights out when you leave tonight. Or be dramatic and wait for 10 p.m.