Residents of Arrow Lakes-Slocan Lake, Boundary, East Kootenay, Elk Valley, Kootenay Lake, Okanagan Valley, and West Kootenay are all being warned to expect 20 to 40 millimetres of rain over the next couple of days.
It comes as unseasonably hot weather is rapidly melting mountain snowpacks, elevating river levels and causing catastrophic flooding in parts of south-central and southwestern B.C.
Environment Canada issued seven special weather statements this morning, including one for the East and West Kootenays, where thunderstorms and showers are expected.
This could occur in areas already suffering from overland flooding, such as Grand Forks today and Friday (May 18).
The storm will move from the Kootenays west toward the Okanagan Valley.
There have been many sad stories in Grand Forks and the surrounding region, where 3,000 people had to flee rising Kettle and Granby rivers.
Among the businesses and homes that have been flooded is the Gem Theatre, which is the province's oldest functioning cinema house.
Built in 1913 as the Empress Theatre, it was renamed as the Gem in the 1950s.
Owners Marius and Maureen Paquet have placed a notice on the theatre's website that it will be closed for "an indeterminate amount of time".
B.C. communities on evacuation alert include Salmo, Barnston Island, parts of Glen Valley, and Carey Point in Chilliwack, where three residents have been ordered to leave their homes.
The B.C. government is encouraging people to donate to the Canadian Red Cross to help flood victims.
Yesterday, Premier John Horgan promised that the province will match donations up to $20 million.
It's possible to make a $10 donation by texting BCFLOODS at 30333.
Donations can also be made by phone at 1-800-418-1111 or by going to this web page.