A child plays at a park in San Mateo, California, the United States, May 28, 2021.

A child plays at a park in San Mateo, California, the United States, May 28, 2021.

A man sniffs at a flower at a park in San Mateo, California, the United States, May 28, 2021.

A woman poses for photo at a park in San Mateo, California, the United States, May 28, 2021. (Photos: Xinhua/Wu Xiaoling)

A woman walks her dog at a park in San Mateo, California, the United States, May 28, 2021.