You wouldn't think a tropical paradise like Hawaii, where countless Americans often head to avoid dreary weather woes back home, would hold any rainfall trophy.
But believe it or not, The Aloha State is home to the wettest spot in the United States -- by nearly a 2-to-1 margin over its mainland challengers.
Mount Waialeale, on the island of Kauai, not only is the American champ with an average of about 450 inches of rain per year, but it's among the wettest spots on the globe. The nearly mile-tall mountain sits amid the juicy tropical trade winds. It's frequently shrouded in clouds as those winds roll up the windward side of the mountains and squeeze out their moisture into nearly constant rainfall.
"If you saved all that water in a graduated cylinder, it would rise to 33 feet tall," writes Ned Rozell with the University of Alaska Fairbanks.
Mt. Waialeale is also home to one of the most significant rainfall gradients around, as on the lee side of the mountains in its rain shadow, annual rainfall averages around… 10 inches per year. (That's about 2 inches less than Tucson, Arizona.)
49th State No Slouch Either
Our other detached state, Alaska, is also home to some impressive rainfall totals, especially in the mountains of the southeastern panhandle.
Other research from Oregon State University and the Alaska Climate Research Center with computer simulations suggests some mountains in southeastern Alaska may rival or even surpass Mt. Waialeale’s rainiest-spot-in-the-U.S. claim. But there haven’t been observations there to confirm it.
Suffice to say, both Hawaii and Alaska have multiple places that get over 10 to 15 feet of rain per year.
What about the Lower 48?
If you're looking for the wettest spot in the Lower 48, it's not Seattle, despite what the jokes might say. But it's not that far away.
Take about a three-hour drive west from Seattle, and you'll find yourself in the Olympic Rain Forest, part of Olympic National Park and the Olympic Mountains on the Olympic Peninsula.
Perched at the front of a relentless jet stream that carries frequent storms off the Pacific Ocean into the Pacific Northwest in the fall, winter and much of spring, the moist winds slam into the southwestern-facing sides of the mountains and squeeze out copious amounts of rainfall.
Mount Olympus averages about 260 inches of rain per year, with 130 to 170 inches per year on average expected in the lower rain forests.
(While you're there, keep an eye out for the 6- to 8-inch banana slugs for an authentic Northwest experience!)
But like Hawaii, the Olympics also have a rain-shadow counterpart known as, aptly, the Olympic Rain Shadow. Just on the leeward side of the Olympics to the northeast sits the small town of Sequim, which boasts only 18 inches of annual rainfall.
It’s the driest spot in Western Washington, with less than half the annual rainfall of Seattle.