Fundamental principles of the weather (8)
I believe the answer is:
I believe this clue is a triple definition!
'fundamental' is the first definition.
'principles' is the second definition.
(I have seen 'First principles ' mean 'elements' so perhaps 'principles' could also mean 'elements')
'of' acts as a link.
'the weather' is the third definition.
(Other definitions for elements that I've seen before include "He and I are two" , "eg Fire, air" , "Constituents, ingredients" , "fire and water, say" , "Rudiments of a subject" .)