Is whenever there is a bluegrass festival adejctive or adverb clause?

The phrase "whenever there is a bluegrass festival" is an adverbial clause.

Here's why:

* Adverbial clauses modify verbs, adjectives, or other adverbs. They tell us *how*, *when*, *where*, *why*, or *to what extent* something happens.

* In this case, the clause "whenever there is a bluegrass festival" modifies the (implied) verb in the sentence, telling us *when* something happens.

For example:

* Whenever there is a bluegrass festival, the town comes alive with music. ("Whenever..." tells us *when* the town comes alive.)

Let me know if you'd like more examples!