Dialect and language are sort of a "coastline problem". You can find variation between two neighboring villages if you like, but at some point you have to draw a boundary around a group of speakers and call it a dialect. I'd assume the common dialect of Santiago, where most people live in Chile, is considered "the Chilean dialect," but it almost certainly sounds different in rural areas.
There are regional variations, but the difference is less than what you would probably expect, applying mostly to intonation/cadence (more marked and melodic in the south, less so in the north) and some vocabulary. Most of the variation in Chilean Spanish is based on socioeconomic status, since Chile's income inequality is rather high.
> [...] intonation (more marked and melodic in the south, less so in the north)
Oddly enough, albeit anecdotal, this is true everywhere; in every country and every continent, people are looser in the south. That said, if it's also true for Chile then it means it's not related to the climate.
> in every country and every continent, people are looser in the south
Fun to think about, but I'm sure there are as many counterexamples as there are examples. In the Germanic languages, for example, no one could deny that Swedish or Norwegian are much more sing-songy than stodgy German.
