Task: Question Answering
Input (English): Background Paragraph: When the subtropical ridge in the Northwest Pacific is stronger than normal, it leads to a wet monsoon season for Asia.[18] The subtropical ridge position is linked to how far northward monsoon moisture and thunderstorms extend into the United States. Typically, the subtropical ridge across North America migrates far enough northward to begin monsoon conditions across the Desert Southwest from July to September.[19] When the subtropical ridge is farther north than normal towards the Four Corners, monsoon thunderstorms can spread northward into Arizona. When suppressed to the south, the atmosphere dries out across the Desert Southwest, causing a break in the monsoon regime.[20]. 
Story: In 2016, the subtropical ridge across North America migrated far enough northward to begin monsoon conditions across the Desert Southwest from July to September, but in 2017 the atmosphere dried out across the Desert Southwest, causing a break in the monsoon regime. Therefore a wet year was followed buy a dry one, and the fires started again. 
Question: Which month of the year was drier, September 2017 or August 2016?
Output (English): September 2017.