The Cowichan Valley is at its best in summer — June to September — when the wineries have their tasting rooms open, the farmers market is in full swing, and the weather is warm and usually dry. July and August are the busiest months on Vancouver Island and the valley sees its share of visitors, but nothing like the crowds at Victoria or Tofino.
Spring is excellent for the Garry oak wildflowers on Mount Tzouhalem and for birding at Somenos Lake. Winter brings grey skies and rain — typical Pacific Northwest — but the swans at Somenos Lake peak in December and January, and the Cowichan Valley stays green and quiet. The Cowichan Valley Citizen's Day festival runs in early summer and is a low-key reason to time a visit.