They're assuming a lot of things here:

* Rain means children watch televsion, no rain means they do not. This is a harsh oversimplification of how parents work.

* Cable TV was correlated to increased autism diagnosis. But what else is correlated to Cable TV? Wealth. And what's correlated to wealth? Getting your kid diagnosed properly in the country where healthcare is not easily affordable maybe? If you think that's a stretch, well, the entire paper is argued on this sort of thin ice.

* Autism isn't generally considered to have "a trigger", but some circumstances like stress can make it more obvious how a someone with autism is different. Autism is one of these things that aren't objectively measured, but often are diagnosed as a result of how annoyed parents are.