Environment Canada has issued a heat warning for the east side of Vancouver Island from Mill Bay to Campbell River.
The federal agency said a ridge of high pressure will raise daytime temperatures to 29 C and overnight lows into the mid-teens. The high temperatures are expected to last though the week.
The heat represents a moderate risk to public health, said Environment Canada.
The agency said risks are greater for seniors, people who live alone, people with pre-existing health conditions such as diabetes, heart disease or respiratory disease, people with mental illness such as schizophrenia, depression or anxiety, people with substance use disorders, and people with limited mobility.
Residents of the affected areas should check on family, friends and neighbours who are at higher risk, the agency said, warning not to leave susceptible people, particularly children, or pets inside a parked vehicle.
