“We’ve had terrible weather all year,” said Debbie Hannevig, the park’s fee operations manager.

The colder temperatures have wreaked havoc with Mother Nature’s schedule here and throughout the West and the Northwest, altering people’s expectations of what they could and could not do this summer. In some areas, visitors were skiing in their bathing suits on the Fourth of July. In other cases, the unseasonable weather may have contributed to various accidents and deaths.

Here, at one of the jewels in the crown of the national park system, hikers have met closed roads and trails too dangerous to try. Rangers are advising hikers to use ice axes and crampons, equipment they normally do not need.

“There has never been this amount of snow, and it stopped us from doing things we would usually do,” Carol Larkin, 66, of Richland said the other day as she and her husband, Dave, 67, changed out of their hiking boots at a rest stop beneath towering Douglas firs near the mountain’s base.

They have hiked here every year since 1990 and wanted to keep up their ritual, even if it was curtailed. They said they encountered some people along the trail who turned back after seeing the snow and others who were unprepared but nonetheless forged ahead.

“I was amazed at some of the people we saw on the trail,” Mrs. Larkin said. “They didn’t have poles. One person was in flip-flops.”