Along with the rest of South West England, Plymouth has a temperate oceanic climate (Köppen Cfb) which is generally wetter and milder than the rest of England. This means a wide range of exotic plants can be grown. The annual mean temperature is approximately 11 °C (52 °F). Due to the modifying effect of the sea the seasonal range is less than in most other parts of the UK. As a result of this summer highs are lower than its southerly latitude should warrant, but as a contrast the coldest month of February has mean minimum temperatures as mild as between 3 and 4 °C (37 and 39 °F). Snow is rare, not usually equating to more than a few flakes, but there have been exclusions, namely the European winter storms of 2009-10 which, in early January, covered Plymouth in at least 1 inch (2.5 cm) of snow; more on higher ground. Another period of notable snow occurred from 17–19 December 2010 when up to 8 inches (20 cm) of snow fell through the period – though only 2 inches (5.1 cm) would lie at any one time due to melt. Over the 1961–1990 period, annual snowfall accumulation averaged less than 7 cm (3 in) per year. July and August are the warmest months with mean daily maxima over 19 °C (66 °F).

What Köppen climate classification does Plymouth possess?