structural:scholar_edition
Climate

An arid region of high xeric scrubland and desert steppe, the canyon and wider basin average 8 in (200 mm) of rainfall annually; the park averages 9.1 in (230 mm). Chaco Canyon lies on the leeward side of extensive mountain ranges to the south and west, resulting in a rainshadow effect that fosters the prevailing lack of moisture in the region. The region sees four distinct seasons. Rainfall is most likely between July and September, while May and June are the driest months. Orographic precipitation, which results from moisture wrung out of storm systems ascending the mountain ranges around Chaco Canyon, is responsible for most of the summer and winter precipitation, and rainfall increases with higher elevation.