Kelowna is classified as a humid continental climate or an inland oceanic climate per the Köppen climate classification system due to its coldest month having an average temperature slightly above −3.0 °C (26.6 °F) and below 0 °C (32 °F), with dry, hot, sunny summers and cool, cloudy winters, and four seasons. The official climate station for Kelowna is at the Kelowna International Airport, which is at a higher elevation than the city core, with slightly higher precipitation and cooler nighttime temperatures. Kelowna has the second mildest winter of any non-coastal city in Canada, after neighbouring Penticton. This is caused by the moderating effects of Okanagan Lake combined with mountains separating most of BC from the prairies; however Arctic air masses do occasionally penetrate the valley during winter, usually for very short periods. The coldest recorded temperature in the city was −36.1 °C (−33.0 °F) recorded on 30 December 1968.
Weather conditions during December and January are the cloudiest in Canada outside of Newfoundland due to persistent valley cloud. As Okanagan Lake hardly ever freezes, warmer air rising from the lake climbs above colder atmospheric air, creating a temperature inversion which can cause the valley to be socked in by cloud. The last time the lake completely froze over was in the winter of 1969. It may have frozen over in the winter of 1986. This valley cloud has a low ceiling, however, and often bright sunshine can be experienced by driving only 20 minutes or so up into the nearby mountains, above the cloud. Summers in Kelowna are hot (sometimes extremely hot) and sunny, with daytime temperatures often exceeding 32 °C (90 °F). The hottest recorded temperature at the airport was 39.5 °C (103.1 °F) on 24 July 1994, and the highest temperature ever recorded in the city was 41.0 °C (105.8 °F) on 4 August 1998, near but not at the airport. Not unusually, heat waves occur in July, August, and even June and September on occasion, where temperatures above 30 °C (86 °F) persist for weeks. During summer, clear, dry air allows night-time temperatures to fall rapidly. The city averages about 380 mm (15 in) of precipitation per year, with about 1/5 of the precipitation falling as snow, the bulk in December and January; however, June is the wettest month of the year.
While some smaller communities such as Blue River and Golden get less wind, Kelowna has the greatest percentage of “calm” wind observations for any major city 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. As shown in the climate chart below, Kelowna has an average high temperature that is above freezing every month of the year – an exceptionally rare phenomenon for an inland Canadian city. In fact, average high temperatures in January surpass those of St. John’s, Newfoundland. Kelowna’s average year-round high temperature of about 14.3 °C (57.7 °F) is also one of the highest in Canada – largely due to the rare combination of high summer temperatures typical of continental climates, along with relatively mild winters – a very rare feature of a continental climate.