A variety of climates and soils combined with the long summer sunlight hours of northern latitudes create prime growing regions, predominantly in the valleys and on the hillsides of areas east of the Cascade Mountain range. Gradually cooling Autumn temperatures in Washington also help wine grapes reach full maturity, while maintaining desirable acid levels. Valleys such as Columbia Valley, Washington State largest of the federally defined ‘American Viticultural Areas’ (AVA), benefit from a continental climate with adequate amounts of rainfall and sunshine.