My mood is like today's weather.

Or I think the weather today.

I feel like the weather outside, sometimes good and sometimes bad (changeable).

My mood is like the weather outside, sometimes good and sometimes bad,

Be good and bad

"changeable" means "changeable" It can also be interpreted as "rain or shine".

It can also be "which is volatile."

We feel the same as the weather today.

Today the weather is fine, and I'm in a good mood. The weather today is as good as my mood.

This is as unstable as people's emotions. Just like people are emotionally unstable.