The Okanagan Valley is BC's largest wine region and second to Niagara in Canada. It runs for some 200 kms from Salmon Arm to the US border. Many of the vineyards are centred around Lake Okanagan between Kelowna and Penticton. The region sits between the Columbia and Cascade Mountains, which protect the vineyards from both maritime influences from the Pacific Ocean and Arctic winds from the north. Instead, the warm continental climate has very low rainfall, and warm sunshine throughout the growing season. A lack of moisture in the air means that the vineyards cool quickly at night, causing the grapes to ripen more slowly and develop acidity and sugars in equal measures.