Bolivia here - I've NEVER in my 14 years living here in two different departments (states) seen a child left alone in a car. It's just unheard of. And we don't even get that much heat or cold either.

The risk is someone can break your window and steal your kid. It's just something that's never done. It would be akin to leaving your child on the street corner while you go up to your apartment to grab the purse you forgot.