Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018. (Photos: Xinhua)

Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018.

Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018.

Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018.

Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018.

Cloud and fog after a rainfall at Huangyaguan section of the Great Wall in the Jizhou District of Tianjin, north China on Aug. 13, 2018.