Thanks for the link, Ed.
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In my part of the world, we have two different systems controlling the weather. One system consists of air masses and air pressure. The other system is the weather demons.

For example, yesterday the Weather Service said we were virtually certain to get heavy rain in the afternoon. I had received a shipment of bare-root daylilies, and they needed to go in the ground.   The DH and I postponed lunch and planted daylilies while we were hungry and tired.

So we got the lilies planted, and of course it didn't rain. The weather demons preferred to watch us drag the hose out and trudge up and down steps in order to use expensive city water to water the lilies in.
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If I were organizing a folk festival, I would have the board members transplant roses (or similar) on the day before the festival so that the weather demons would hoard the rain. It's not a surefire method, but then neither is scientific weather prediction.