Video posted online has shown beach-goers in Novosibirsk, Siberia, huddling desperately under umbrellas, as cherry-sized hailstones pelt them mercilessly.
Weather has been unusually extreme across much of Russia this summer, with snow hitting parts of central Russia that rarely dip to freezing temperatures in summer.
Nineteen-year-old business owner Nikita Dudnik (https://vk.com/nik_dudnik) who was on the beach when the storm hit, filmed the quick change in conditions which forced people to run out of the sea and off the beach to seek cover.
"As soon as we got there, it started raining and hailing. I saw people panicking and I realised this was something extraordinary," Dudnik told the Associated Press on Monday.
He added, "it continued hailing for about 15 minutes, and when we left the site we were still being pelted by the hail."
"We tried calling the emergency services to put out a warning that it was not safe to come here, but all lines were busy," Dudnik told the AP in a phone interview.
Russian authorities have opened an investigation into the deaths of two children during the severe hailstorm in Siberia.
The Investigative Committee said in a statement published online on Monday that two young girls aged three and four died on Saturday in the lakeside town of Bredsk, not far from the large Siberian city of Novosibirsk.
The two girls died after sustaining traumatic brain injuries when a tree fell on their tent, where they were taking shelter from the storm along with their families.