While record snowfall and single-digit temperatures pummel much of the United States, an extreme snow drought and unusually warm weather are keeping skiers off the mountains, snowmobilers off the trails and water out of the rivers across much of the West.

In many places famed for deep natural snow, including Park City, Utah; Vail, Colo.; and central and eastern Oregon, much of the ground is bare or blanketed with mere inches rather than feet of snow.

The extent of snow-covered ground is at a record low. Instead of the typical winter sports, people across the West are still hiking and biking in 50- and 60-degree weather.

Many are closely watching snowpack measurements because snow in the mountains provides natural storage for water in the arid West. The runoff will be slowly released in the coming months, acting as a primary water resource for millions of Western residents and for irrigating farm fields and filling trout streams and reservoirs.

The stunning decline in snowpack in the Colorado Rockies and the Colorado River basin adds to the 26-year-long megadrought in the region, which has led to extremely low levels in the two largest reservoirs on the Colorado River. And the assessments represent the latest backdrop for tense negotiations this year between Upper and Lower Basin states on how the river will be managed in the future.

What’s occurring across the region isn’t easily explained. Scientists have found that it is difficult to attribute the snow drought entirely to climate change. But the changes are striking.