Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows a helicopter flying over the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the flames and dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)

Photo taken on Aug. 19, 2020 at the Windy Hill Open Space Preserve of San Mateo County shows the dense smoke of wildfires in San Francisco Bay Area, California, the United States. Wildfires forced closure of more than 20 parks and evacuation of tens of thousands of residents across the San Francisco Bay Area in northern California, officials said Wednesday. (Photo by Dong Xudong/Xinhua)