Kelowna - Geography and Climate

Geography and Climate

Kelowna has a semi-arid climate (Köppen climate classification BSk), with dry, sunny summers, cold, cloudy winters and four seasons. The official climate station for Kelowna is at the Kelowna International Airport, which is at a higher altitude than the city core with slightly higher precipitation and cooler temperatures. Okanagan Lake as well as the blocking barriers of the Canadian Rockies and the Columbia Mountains to the northeast tend to moderate the winter climate, but Arctic air masses do occasionally penetrate the valley during winter, usually for very short periods (coldest recorded temperature of −36.1 °C (−33.0 °F), on December 30, 1968).

Summers are hot and sunny, with daytime temperatures often exceeding 35 °C (95.0 °F). The hottest recorded temperature at the airport was 39.5 °C (103.1 °F) on July 24, 1994. A higher temperature 40.0 °C (104.0 °F) was officially recorded twice at the Burnett Nursery climate station, closer to the downtown area, in 1998. During summer clear, dry air allows night-time temperatures to fall rapidly. The city averages about 300 millimetres (12 in) of precipitation per year, with about 1/3 of the precipitation falling as snow, the bulk in December and January; however, June is the month of greatest rainfall. The inherent dryness of Kelowna's climate is a factor in the forest fire risk as, for example, during the Okanagan Mountain Park Fire of 2003, a large residential evacuation (over 30,000 residents) was ordered.

Although Kelowna averages 300.5 hours of bright sunshine in July (61% of daylight hours), the winter months are mostly overcast due to the presence of low-level Pacific moisture pushing eastward toward the surrounding mountains and getting trapped in the valley; thus, Kelowna averages only 40.3 hours of bright sunshine in January (for comparison, consider 120 hours at Winnipeg, Manitoba and Miramichi, New Brunswick, which both have much colder winter temperatures).

Kelowna has the greatest percentage of "calm" wind observations in Canada (39% of the time). The four-year average wind measured at the airport has been less than 5 knots on average 10/12 months of the year between 2008 and 2011.