Waterfall rainbows: when and where to stand
Short answer: A waterfall rainbow needs the sun behind you and lower than about 42°, shining on the spray in front of you. So each viewpoint has its own rainbow hours, and they shift with the seasons. Pick a waterfall to see the times for your date.
Victoria Falls
Today: Best rainbow from Zambia side, Knife-Edge Bridge, 05:55–10:50 (strongest around 06:00), if the sun is out.
Iguazú Falls
Today: Best rainbow from Devil's Throat walkway (Argentina), 06:10–18:45 (strongest around 06:40), if the sun is out.
Niagara Falls
Today: Best rainbow from Canadian side, facing the American Falls, 12:30–16:40 (strongest around 14:20), if the sun is out.
Skógafoss
Today: Best rainbow from In front of the falls, by the pool, 10:05–16:10 (strongest around 12:50), if the sun is out.
Seljalandsfoss
Today: Best rainbow from Behind the curtain of water, 10:05–13:20 (strongest around 10:10), if the sun is out.
Gullfoss
Today: Best rainbow from Lower path at the edge of the falls, 10:10–16:15 (strongest around 16:10), if the sun is out.
Dettifoss
Today: Best rainbow from East bank viewpoint, 10:00–12:45 (strongest around 10:00), if the sun is out.
Rhine Falls
Today: Best rainbow from Laufen Castle platforms (south bank), 08:35–16:40 (strongest around 15:20), if the sun is out.
Yosemite Falls
Today: Best rainbow from Lower Yosemite Fall footbridge, 08:05–15:30 (strongest around 13:35), if the sun is out.
Vernal Fall (Mist Trail)
Today: Best rainbow from Mist Trail below the fall, 11:20–15:30 (strongest around 15:20), if the sun is out.
How we calculate it
A rainbow is a circle of about 42° around the point exactly opposite the sun. You only see the part of that circle that falls on sunlit spray, so it needs the sun behind you and lower than about 42° above the horizon. For every 5 minutes of the day we place that circle in the sky and check how much of it lands on the spray seen from each viewpoint.
Victoria Falls also has a moonbow on full-moon nights; see full-moon experiences.