Yeah, I believe the phrase is short for the weather:

What’s the weather doing?

It is raining.

Context matters. Always. One person can use a word and it will be not racist, another can use the same term and it will be racist. You should ask the person what they define as “civilized”. Their reasoning is your answer.

2010, simply because of how english works.

If you say 2001 as twenty one, it’s confusing. Same goes all the way up to “twenty nine”.

And it’s more garbled and slower to say “twenty oh one” vs “two thousand one”, especially if you’re speaking quickly.

“Twenty ten” and up, however, starts making sense as a different piece of information and can be used easily.