The average annual temperature in Vancouver is 11.0 °C (51.8 °F) downtown and 10.4 °C (50.7 °F) at YVR airport in Richmond. This is one of the warmest in Canada. Greater Vancouver is in USDA plant hardiness zone 8,^[1] similar to other coastal or near-coastal cities such as Seattle, Portland, Amsterdam, and London, as well as places such as Atlanta, Georgia and Raleigh, North Carolina, far to the south (though these locations have far more growing degree days). The semi-mild climate sustains plants such as the Windmill Palm. Vancouver’s growing season averages 221 days, from March 29 until November 5. This is 72 days longer than Toronto‘s, and longer than any other major urban centre in Canada.^[2]

Despite normally semi-mild winters due to the onshore air flow over the North Pacific Current, occasional cold arctic outflows (sinking cold continental air that flows down through the Fraser Valley coastward) in winter can sometimes last a week or more. These arctic outflows occur on average one to three times per winter. The coldest month on record at Vancouver International Airport was January 1950 when an arctic air inflow moved in from the Fraser Valley and remained locked over the city, with an average low of −9.7 °C (15 °F) and an average high of only −2.9 °C (27 °F), making for a daily average of −6.3 °C (20.7 °F), 10 °C (18 °F) colder than normal. The coldest temperature ever recorded in the city was −18.3 °C (−1 °F) on December 29, 1968. ^[3] The coldest temperature across Metro Vancouver, however, is −23.3 °C (−10 °F) recorded on January 23, 1969.^[4]

With snow being an infrequent occurrence over a typically mild winter, many cold hardy flowers remain in bloom and are common in gardens and office exteriors throughout the winter. The arrival of spring is often first noticed in February with slightly milder temperatures and the return of flowering perennials. It’s also not uncommon for cherry blossoms to begin blooming later in the month, as was seen prominently during the 2010 Winter Olympics.

The Greater Vancouver region is also subject to significant variations in summer temperatures, which can differ by as much as 5–10 °C (9–18 °F) between inland areas of the Fraser Valley and the ocean-tempered coastal regions when localized on-shore breezes are in effect. Conversely, winter temperatures tend to be cooler inland by a couple of degrees.