modifying an adjective

Hi,

It is known to me that only adverb can modify an adjective but I have been modifying weather words/terms/adjectives?? like "sunny" with words like "sizzling" and "boiling". Do you call them an adverb like "very"?? I have used the word/adjective "bright" to modify "sunny". Is that wrong? I think we can use it in a pre-adjective position like this, "the bright, sunny weather" but it seems wrong to write "The weather is bright sunny" in a predicate position. Only an adverb can modify an adjective? I htink an article can modify it too.