The climate, according to the Köppen climate classification, is semi-arid (BSk) with summers that are generally hot and dry. Daily temperatures in July and August average above 30°C (86°F), with overnight lows of around 14°C (57°F) with low humidity. September and October are usually dry and sunny with cool mornings. Winters are short and mild, but can be cold for brief periods during arctic outflow conditions. Spring arrives earlier than other parts of the Okanagan.
The table below includes temperature records for the "Osoyoos CS" station (with records from 1990–2011), and precipitation values from the "Osoyoos West" station (with records from 1971–2001). It is important to note that these temperature records are only go back as far as 1967, meaning that higher and lower extremes may have occurred. Of note, the town of Oliver just over 20 km north of Osoyoos reached 43.9°C on July 16, 1941 the same day that Lytton and Lillooet hit the highest temperature ever recorded in British Columbia of 44.4°C.
During the summer months, the southern Okanagan Valley is among the hottest areas in Canada, and Osoyoos often reaches the highest daytime temperature of any location in Canada. Temperatures typically reach the upper 30s (Celsius) (95-104°F) in the summer for short periods of time. Although it is hot, the humidity is low and nights are generally pleasant. Winters are generally dry and cool, but are usually mild compared to directly adjacent regions.
The USDA places Osoyoos in Plant Hardiness Zone 7a
