A lightning strike has injured two tourists who were standing near the rim of the iconic Horseshoe Bend in Arizona’s Glen Canyon National Recreation Area, the National Park Service says. 

The incident happened on Monday around 4 p.m. and involved two women – a 22-year-old from the Netherlands and a 23-year-old from Australia. 

"Visitors are advised to use caution while visiting exposed outdoor areas and be aware of changing weather conditions. Thunderstorms are most frequent and severe during the monsoon season, which is typically mid-June through September in Arizona," the NPS said in a statement. "If you hear thunder, you are at risk of getting struck by lightning and should immediately seek shelter in a vehicle or building." 

The NPS said the two tourists "sustained injuries" in Monday’s incident and were airlifted to St. George Regional Hospital in Utah. 

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The NPS describes Horseshoe Bend as a "social media darling" and one of the "most recognized and visited places in Glen Canyon National Recreation Area." 

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"Below the rim, the Colorado River makes a wide sweep around a sandstone escarpment. On its long downward journey to the sea, the river meandered, sometimes making wide bends, but always seeking the path of least resistance. Around 5 million years ago, the Colorado Plateau uplifted and the meandering rivers that crossed the ancient landscape were trapped in their beds," it says on its website. "Over time, the rivers cut through the uplifted layers of sandstone. 

"Here at Horseshoe Bend, the Colorado River created a roughly 1,000 ft. deep, 270º horseshoe-shaped bend in Glen Canyon," it adds.