Answer:
Assuming that the bolded word is yet, the answer is: it is a coordinating conjuction.
Explanation:
A coordinating conjuction is a word that joins two words or two phrases, of equal grammatical rank. In English, there are only seven coordinating conjunctions: for, and, nor, but, or, yet, so.
In this case, the word yet is joining to phrases: 10 inches of rain had fallen and the downpour continued.
