there's no need to get too technical about the process. i think the native americans had it right with their rain dances, and the way they approached the weather.
in my experience, if you invite the rain, the way you would invite a friend to dinner, and then get into the feeling of the blessed rain feeding the earth and nourishing all the little green living things, your chances are pretty good. and of course be sure and thank the rain for coming.
i've done this for years, because i've worked outside for most of my life i would simply ask for 8 hours of clear weather at the worksite, and i almost always got it. i can remember driving home several times and just getting a mile or two away from the jobsite, i'd run into a shower or thunderstorm, or sometimes everything would be soaked because one had just passed thru.
i reseeded part of our back yard this spring, so i asked for extra rain until the seedlings had taken root. we got rain every day for about 10 days, and i overheard one of the local meteorologists puzzling over all the "unexpected" rain we were getting! :d
If you wish to save the world, work on yourself. That is our main suggestion to you. ~Quo
The greatest gift you can give anyone, is the example of your own life working. ~Orin