The following forecast is from Accuweather (http://tinyurl.com/y8tmvkuj), which is in line with Environment Canada (https://weather.gc.ca/saisons/prob_e.html). British Columbia: Summer is expected to be drier than normal for most areas, including Vancouver. The exceptions may be the BC Rockies the second half of the summer due to a greater than normal amount of thunderstorm activity. Streamflows are expected to be near normal for most of the summer. I also expect more showers than usual across the far northwest portion of the province. In terms of temperatures, ocean water surface temperatures off the coast are running lower compared to previous years and this should keep temperatures close to normal along the coast. However, the projected drier weather pattern across the southern interior favors a higher number of days above 30 degrees Celsius compared to normal.
Okanagan Lake Levels
As everyone knows, Okanagan Lake is at historic levels – 343.16, as of May 31. The graph below shows the lake water levels over the past year (since January 1, 2016). The green line is the water level, the center blue line is the 30-year average (more or less the target they are trying to reach), and the blue lines on either side are the 25th and 75th percentile, meaning that 50% of the time, the water level falls between this range.
Osoyoos Lake Levels
Osoyoos Lake is also far exceeding its normal levels. It is currently 914.3 ft elevation above sea level. The water spills over the weir on Zosel Dam when the lake is at 913 ft. The current levels are due in part to extra flows from upstream, and the Similkameen obstructing flow downstream. As you can see from the Similkameen River graph (bottom), when the river level falls, the lake level falls slightly.