Louis Tomlinson was forced to cancel a gig after 'golf ball-sized hail' started pelting the audience.
Crowds of fans piled into Red Rocks Amphitheatre in Colorado on Wednesday (21 June), when the weather turned. Have a look for yourself:
The National Weather Service issued a 'Severe Thunderstorm Warning', with huge hailstones raining down.
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And despite their efforts to seek shelter from the storm, almost 100 fans of the former One Direction singer suffered injuries such as broken bones.
In a statement about the storm, West Metro Fire Rescue said: "A total of 80 to 90 people treated on scene. Injuries include cuts and broken bones."
At the time, the venue posted a statement confirming the show had been canceled: "Tonight's show has officially been postponed.
"Please be safe exiting the amphitheatre - we'll have more information for ticket holders soon."
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Following the announcement, Tomlinson took to social media to apologise to his fans.
In a post to Twitter, the 31-year-old said he was gutted at having to pull it.
"Devastated about the show tonight, hope everyone’s OK, I’ll be back," the singer wrote.
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"Even though we didn’t play the show I felt all of your passion! Sending you all love!"
Upset fans later took to social media to share some of the injuries they suffered.
One concert goer said: "Tonight was the scariest night of my life. It started pelting people with hail at Red Rocks and my sister and I luckily found shelter under a sign.
"I am bleeding and have huge bumps on my head from the hail. Hoping everyone made it out safely."
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Another commented: "Scariest hail storm I’ve ever been caught in. This show should have been canceled an hour ago."
While someone else shared a photo of a chunk of hail, along with the caption: "My dad took this right after I was safe backstage. It was straight out of a horror movie."
After he heard about the injuries, Tomlinson released a lengthier statement in which he assured fans that he wanted to go ahead with the concert at some point in the future.
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"Sending all my love out to everyone that was affected by the extreme weather at Red Rocks last night," he wrote.
"I hope everyone has made it home safely and anyone injured is on the mend, it was devastating to see so many of you affected.
"I want to thank the speed and care of my touring personnel and the first responders who worked tirelessly last night to help care for everyone affected in what was such extreme circumstances.
"We're working hard to find a rescheduled date for the show so please hang onto your tickets until we have more info.
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"Get well soon, and I'll be back at Red Rocks soon! Louis x."
UNILAD has contacted Red Rocks Park and Amphitheatre for a comment.
Dominic Smithers