Feeling under the weather

What does that expression mean?

We’re always under the weather, considering that the climate conditions are reflected in the sky, so all of us wake up every day feeling “under” the weather…. However, stupid people use this expression to express a mood or a feeling, like when you’re sad or going to be sick.

I really can’t put my finger on it.
I feel under the weather all the time… if the day starts like today: cloudy, cold, gloomy… I’ll most sure will feel under the weather… a “pilarsicle” working with the only purpose to be back at my comfy house, warm and toasty.

I’ll have to come up with a different phrase to express my “comfort (or uncomfortable) situation” when I’m coming down with a flu or something… maybe I can say: I’m feeling like the weather… but that will only work if it’s an awful day… the sun wouldn’t replicate my state if he’s too shiny and I’m too ‘grey’. 

I could say: I’m feeling opposite to the weather.. if it’s too sunny for my ‘sick’ state.

That’s it… Like or Opposite.
I think it’s catchy and a bit less moronic that Under.

So today, I’m definitely feeling LIKE the weather… I’m not coming down with the flu, but I’m sleepy and cold, I want to be at my home, cuddling with my pillow and burrowing under the covers.

I’ll love to be feeling OPPOSITE to the weather.

We're definitely UNDER it… but that doesn’t explain to you how I’m feeling at all.

To be more specific, I'm like the weather, wanting to be opposite and definitely under.