Today

It has been snowing since this morning.
My children are excited, but I'm not. Because because I hate the cold.

'because' is a word you use to join two phrases/sentences together, so it should not be used with only one sentence:

I'm not excited because I hate the cold. (O)

I'm not excited. Because I hate the cold. (X)

You can also switch the two parts around:

Because I hate the cold, I am not excited. (O)
Because I hate the cold. I am not excited. (X)