Being lucky is an option. ("I shall cause it to rain" and it just so happens to rain.)
Outsmarting your client is another option. ("I shall cause it to rain... tomorrow" - meanwhile, you have used meteorology to predict that it will rain tomorrow.
Lies and rumors are a third option. ("That magician can make it rain! I saw it with my own eyes!" meanwhile it's actually just a baseless rumor which has circulated around town for a while.)