Aerial photo taken early Dec. 1, 2019 shows clouds covering the county seat of Ning'er, southwest China's Yunnan Province. (Xinhua/Yang Zongyou)

Visitors take photos of clouds covering the county seat of Ning'er, southwest China's Yunnan Province, Dec. 1, 2019. (Xinhua/Yang Zongyou)

Photo taken early Dec. 1, 2019 shows clouds over the county seat of Ning'er, southwest China's Yunnan Province. (Xinhua/Yang Zongyou)

Photo taken early Dec. 1, 2019 shows fogs over mountains in the county seat of Ning'er, southwest China's Yunnan Province. (Xinhua/Yang Zongyou)

Clouds cover the county seat of Ning'er, southwest China's Yunnan Province, early Dec. 1, 2019. (Xinhua/Yang Zongyou)

Clouds cover the county seat of Ning'er, southwest China's Yunnan Province, early Dec. 1, 2019. (Xinhua/Yang Zongyou)

Clouds cover the county seat of Ning'er, southwest China's Yunnan Province, early Dec. 1, 2019. (Xinhua/Yang Zongyou)

Clouds cover the county seat of Ning'er, southwest China's Yunnan Province, early Dec. 1, 2019. (Xinhua/Yang Zongyou)

Clouds cover the county seat of Ning'er, southwest China's Yunnan Province, early Dec. 1, 2019. (Xinhua/Yang Zongyou)

Visitors take photos of clouds covering the county seat of Ning'er, southwest China's Yunnan Province, Nov. 30, 2019. (Xinhua/Yang Zongyou)