A wilderness patrol ranger at Yosemite National Park encountered three separate groups of hikers lost among snow-covered trails as darkness fell last week.

The hikers were returning to the Tuolumne Meadows area after making the trip to Clouds Rest, and the ranger found them several miles out in the backcountry on July 1.  

By the time the ranger rounded up the groups and returned them to their cars, it was 11 p.m. 

"One hiker was suffering from altitude sickness and another was asthmatic," according to a blog post from the park posted on July 6. "None of the hikers was enjoying their experience."

RELATED VIDEO: Caltrans crews work to clear Tioga Pass Road

May 20167: Road crews are working to clear Tioga Pass after a winter season that brought a record-breaking snowpack.

Media: Caltrans

A brutal winter built up a massive snowpack in the Sierra Nevada this year, and areas of the park above 8,000 feet elevation remain under snow.

Tioga Pass Road, which passes through Tuolumne Meadows where many popular hiking trails start, often opens by Memorial Day. This year it saw the latest summer opening in two decades and only became accessible to motorists on June 29.  

Park spokesperson Scott Gediman warns that hikers in the Tuolumne area need to have experienced route-finding skills and the proper equipment including a detailed topographical map and compass in case your GPS can't get a signal. 

"The road is open and that's great, but we're still calling it spring conditions," Gediman says. "We have a huge snowpack. It has been warm but there's still significant amounts of snow on the trails. Some of the signs are covered. Also the streams are running fast and crossing conditions can be dangerous.  We have some damaged bridges. We haven't been able to get a lot crews into the backcountry to fix them because there's so much snow."