Terrible news out of China ... where 21 elite athletes died during a 62-mile, ultra-marathon race when the group got caught in a freezing storm that appeared out of nowhere.
The event -- known as the Huanghe Shilin Mountain Marathon -- began Saturday morning when the weather was sunny and nice.
Most of the 172 runners had anticipated normal weather conditions and showed up to the race in shorts and t-shirts, typical running garb.
But, things took a sudden turn just after noon around the Yellow River Stone Forest -- when a freezing cold storm moved in, punishing the runners with a barrage of hailstones, rain and icy winds.
Some of the athletes reportedly recognized the deadly conditions and tried to seek shelter ... others apparently tried to push through it (remember, these athletes are some of the toughest people in the world).
According to reports, some of the runners began experiencing hypothermia -- and eventually, the organizers pulled the plug on the race.
Realizing the situation was turning deadly, a 1,200 person search party was dispatched to locate and rescue all of the athletes. Officials also used thermal-imaging drones to find the participants ... but it proved to be too late.