People cool off at the Splash Island of Toronto Zoo in Canada, on June 30, 2018. Toronto issued a heat warning on Saturday as the temperature hit 35 degrees Celsius. (Xinhua/Zou Zheng)

Kids cool off at a wading pool in Toronto, Canada, on June 30, 2018. Toronto issued a heat warning on Saturday as the temperature hit 35 degrees Celsius. (Xinhua/Zou Zheng)

A boy cools off at the Splash Island of Toronto Zoo in Canada, on June 30, 2018. Toronto issued a heat warning on Saturday as the temperature hit 35 degrees Celsius. (Xinhua/Zou Zheng)

A girl cools off at a wading pool in Toronto, Canada, on June 30, 2018. Toronto issued a heat warning on Saturday as the temperature hit 35 degrees Celsius. (Xinhua/Zou Zheng)