The head of Android design in Google, Matias Duarte, posted a great post to G+ about the role of consistency and Android design guidelines. The post is a good read and relates directly to the discussion about the Yahoo! Weather app.
“Consistency and conventions are there to help your users. They help users get things done and not worry about how to get things done. Design guidelines are there to help you understand the consistency and conventions, especially if you’re not from around here.” -Matias Duarte