The climate of Seattle is temperate, classified in the Mediterranean zone by the main climatic classification (Köppen: Csb) but some sources put the city in the oceanic zone (Cfb). It has cool, wet winters and mild, relatively dry summers, covering characteristics of both. The climate is sometimes characterized as a "modified Mediterranean" climate because it is cooler and wetter than a "true" Mediterranean climate, but shares the characteristic dry summer (which has a strong influence on the region's vegetation). The city and environs are part of USDA hardiness zone 8b, with isolated coastal pockets falling under 9a.