Gardening in Island County can be a very rewarding experience. WSU Extension provides objective, research-based and credible information you can use in your garden every day. In addition to answering your gardening questions the Extension office, with their team of volunteer Master Gardeners, can help you with plant identification, and plant problem diagnosis.
Popular Factsheets for the Island County Gardener
Pollination and Pollinator Protection
General Gardening Information
According to the Sunset Western Garden Book, Island County is in Climate Zone 5. Mild ocean air moderates winters in this area. The region produces some of the finest rhododendrons, Japanese maples and rock garden plants anywhere.
Growing Season: Between 200 and 250 Days
Rainfall: Lower elevations, 13″; Higher elevations, 22″
Average Temperatures: Winter High 40.4°/ Low 25.8°; Summer High 93.3°/Low 59.1°
Frost Dates: Generally the last date of freezing temperatures for the islands is mid April and the first frost of the year is around the end of October.
Climate: Island County climate is highly influenced by the maritime air in our region. The Olympic Mountians creates a rain shadow that alters the rainfall patterns considerably on Whidbey and to some extent on Camano Islands. The region just north of Coupeville (Pt. Partridge) is impacted by the rain shadow the most and is one of the driest areas in the county, approximately 18 to 19 inches per year on average. However, regions North and South have much higher rainfall levels. South Whidbey at Clinton ranges in the 30’s and areas North of Oak Harbor can be in the high 20’s. Camano Island generally ranges in the mid twenties to mid 30’s. Some measurable precipitation is likely 120 days of the year Temperatures can vary a great deal around the islands, however it is typical that temperatures are several degrees cooler on the islands than on the mainland of the Puget Sound region. At Coupeville average daily temperatures range from the low 70s in the heat of the summer to mid 30’s for lows in the winter. Extremes have ranged from the high 90’s to below freezing during the year.