It's relatively simple to make it rain. If you have clouds with enough water in them to rain. If the clouds don't have enough water in them to rain you can seed them all you like, nothing will happen.
People don't understand how much energy is locked up in weather. It basically makes human power generation look trivial. So no, governments aren't going around creating new weather systems.
Steering existing weather patterns might be slightly more feasible, but is still going to take an unreasonably large power generation capability, and is still subject to the chaos maths Zen mentioned. Is it going to go where you want it, or is it going to spin back on you?
We don't need government conspiracies to alter weather patterns, climate change has already done that and the predicted effects include higher intensity storms happening with increased regularity. My father was involved with flood control work as part of his engineering job and he said that by the time he retired at the end of the '80s you could already see that the predicted frequencies of storms were wrong - or as he put it "we were getting a hundred year storm once a decade".