Aerial photo taken on May 19, 2018 shows clouds over the Laoshan mountain scenic zone in Qingdao, east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on May 19, 2018 shows clouds over the Laoshan mountain scenic zone in Qingdao, east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on May 19, 2018 shows clouds over the Laoshan mountain scenic zone in Qingdao, east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on May 19, 2018 shows clouds over the Laoshan mountain scenic zone in Qingdao, east China's Shandong Province. (Xinhua/Guo Xulei)

Aerial photo taken on May 19, 2018 shows clouds over the Laoshan mountain scenic zone in Qingdao, east China's Shandong Province. (Xinhua/Guo Xulei)