Who's asking: Me
I first heard this rumor from an old boyfriend whose father was a feed salesman, and the idea of it enchanted me -- I could imagine entire flocks of turkeys looking at the sky, then falling on their backs as the water filled their beaks and drowned them.
Sadly, it's not true. Basic turkey anatomy prevents it. Turkeys' eyes are on opposite sides of their heads, so they don't look up in the same way we do (or, for you Shaun of the Dead fans, the same way dogs do). Instead, they tilt their heads sideways to see things above them. This does not expose their nostrils to rainfall, any more than their beaks would already be exposed.
That said, turkeys are seriously stupid animals. Wild turkeys are dumb -- I have come close to hitting more than one that was just strolling across a road, oblivious to cars -- and domesticated turkeys are even dumber, as they've had all their survival instincts bred out of them. Snopes.com describes incidents in which domestic turkeys, startled, have panicked and run to a corner or a fence, where they've piled up and smothered each other. I am a bad, bad person for giggling at that mental image. I do object in principle to factory farming, and buy organic meats when I can; but I am also grateful that turkeys are just so darn tasty, and dumb enough to let us eat them.
Happy Thanksgiving, everybody.