I was talking recently with a new friend and made an off-hand comment about stopping the rain long enough to get somewhere dry, when she gently chastised me for even considering it, quoting the line about "not knowing what it may cause elsewhere".
That idea, believe it or not, comes from an old episode of I Dream of Jeannie. I haven't found any reference predating the show to anyone believing it's true, but that's not the whole basis of my belief that it's just bunkum.
I live in California, on the west coast of the United States. In the midwest, there are tornadoes and hail storms that we don't have here. On the east coast, there are hurricanes that we don't see here. I can have a perfectly sunny day while on the east coast they have 90mph winds with driving rain and homes being ripped apart and floating away. Their weather doesn't affect my weather patterns.
So, if natural weather patterns on the east coast or in the Sahara Desert have no impact on my weather here, why would anyone expect any weather magic I do to affect my local environment to have a greater impact than Nature herself? It's not logical, and the facts don't back up the myth.
I have about a 70-80% success rate with the weather magic I've done over the years, and it's stayed pretty consistent. But I don't kid myself - if Mother Nature decides we're going to have a certain type of weather, and she's insistent about it then there's nothing I can do to change it. I'm humble enough to know my limits!
I don't expect everyone to believe me, I think some people need external, artificial limits to their belief structures. But let go of the fear about it for goddess' sake, I'm not going to single-wandedly bring about Global Warming or the next Ice Age.