Area resources director Stu Cartwright says important salmon-bearing rivers such as the Fraser, Thompson and Nicola are all affected.
He says juvenile salmon along the Thompson and Fraser systems sometimes spend more than a year in those waters and will be stressed, as will adult fish that begin arriving soon to spawn.
Cartwright says juvenile salmon in the Nicola River are also at risk.
He says serious problems begin when river water reaches 20 degrees or higher.
Warmer waters carry less oxygen, but fish need more oxygen as waters heat up, harming or killing salmon stocks if rivers get too hot. (CHNL)
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