Children cool off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)

A child cools off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)

A girl cools off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)

A child cools off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)

Children cool off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)

A boy cools off in the fountain at Grand park in downtown Los Angeles, the United States, July 24, 2018. Health officials issued a heat alert for Los Angeles County's inland valleys Monday, warning that a multiday heat wave this week will put the community's most vulnerable residents at risk. (Xinhua/Zhao Hanrong)