Kids cool down at a park in Hamilton, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

Kids play with water in a wading pool in Mississauga, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

People cool down at a park in Hamilton, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

A kid plays with a toy water gun in a wading pool in Mississauga, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

A kid plays with water in a wading pool in Mississauga, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

Kids play with water in a wading pool in Mississauga, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)

Kids play with water in a wading pool in Mississauga, Ontario, Canada, July 5, 2019. Environment Canada issued a heat warning for Southern Ontario on Friday. (Xinhua/Zou Zheng)