Talking about future weather conditions
I want to say the weather will be beautiful tomorrow
Do I say el tiempo estará hermoso mañana o el tiempo será hermoso mañana?
I think Ser is more for pernament conditions where as estar is temporary. So if weather is temporary, would I use estará?
3 Answers
I agree with Jubilado. The common way is to use "hacer" with various expressions.
To express the weather will be "beautiful" I'd say "mañana el clima va a ser hermoso"
O "va a ser un día muy hermoso. " Some things just don't translate well word for word.

Ramona:
If you want to know about "ser" and "estar" read my thread on the subject. I got many many compliments on it.
Link to ser and estar by Daniela
Now that you have good answers to your question, I have difficulty letting a temporary vs. permanent comment lie.
May because era niño, soy adulto y algún día estaré muerto. Which of the three is (will be) permanent?
Estar is for conditions. What things are being.
Ser is for defining characteristics. What things are.
Bananas yellow. Los platános son amarillos.
The ones I buy start out green (están verdes) for a while before they are yellow for that short period before they turn black and nasty (están podridos).
But to us, being yellow is what defines a banana, as short as that period is in its existence.