There is no such thing as "chemtrails". Period. Codpiece provided good information. Instead of running down the conspiracy theory path, a path paved with bullshit, pseudo-science, and anti-science, people should educate themselves with...science. Science is merely a rigourous methodology applied to various facets of the natural world in order to properly understand it. Do some research on meteorology, atmospheric science, and what is a contrail? There are enough jaw-dropping wonders in nature without adding fantasy and paranoid conspiracies into the mix.
And, yeah, the climate (weather patterns over time) is changing. Every month and every year over the past several years have been setting temperature records. This affects wind patterns, the jet streams (atmospheric rivers of air), atmospheric moisture, storm intensity, drought conditions in one part of the country and flooding rainfall in another. and so on.