BEIJING—At least 21 people were killed when extremely cold weather struck during an ultramarathon on Saturday in rugged Gansu province in northwestern China, state media reported on Sunday, sparking public outrage over the lack of contingency planning. Another eight had been injured, officials from Baiyin city told the press at 8 a.m. Beijing time on Sunday. The 62-mile (100-kilometer) cross-country race kicked off on Saturday morning with runners clad in t-shirts and shorts under overcast skies, according to photographs posted on the social media account of the Yellow River Stone Forest scenic tourist site in Jingtai, a county under the jurisdiction of Baiyin city. “At around noon, the high-altitude section of the race between 20 and 31 kilometres was suddenly affected by disastrous weather. In a short period of time, hailstones and ice rain suddenly fell in the local area, and there were strong winds. The temperature sharply dropped,” said Baiyin …