This article explains how rather than con/chemtrails can be used to manipulate weather patterns. They can be used to predict it. Thats right predict it. Here is the article for you to read for yourselves.
Clear skies ahead
By: Gavin Pretor-Pinney
It was just before the second world war that “contrails” — condensation trails from aeroplanes, which are also known as vapour trails — started to appear in our skies. Contrails couldn’t be more different in their appearance from natural clouds. They are long, straight, and often have abrupt angles where the plane’s flight path takes a diversion. They can hang in the sky for some time when there’s enough moisture up at cruising altitude.
Aesthetically, I don’t see contrails as worthy of our appreciation as much as the natural clouds. It’s the formless, chaotic beauty that clouds bring to our skies that make them something to appreciate. Contrails are orderly lines of progress. They can be beautiful at times when several crisscross each other and hang around, and spread out in the high winds, like a tartan, but most of the time I see them as being in opposition to natural clouds.
However, they can be useful for predicting changes in the weather. You may have a blue sky, with no clouds visible, but you may notice that the contrails are hanging around; this usually means there is a change in the weather coming – that in 24 hours or less, it might start to cloud over and you might start to have some gradual rain.