Vineyards in Horse Heaven Hills are on the south-facing slopes along the Columbia River. The river aids in moderating the extreme fluctuations that affect the Columbia Valley, making HHH less prone to frost. The intense wind is also a major factor, producing grapes with thicker skins and reduced fungal pressure. It is also one of the driest (of an already impossibly arid area) with an average of only 7-9 inches of rain per growing season.