California is bracing for a potential return to drought conditions as a heat wave sweeps across the northern part of the state. The unseasonably warm temperatures are rapidly melting the Sierra Nevada snowpack, which is currently at a critically low 18% of its normal level. This situation has forced early closures at several ski resorts, including Mount Shasta Ski Park and Sierra-at-Tahoe, and is raising serious concerns about the state's water supply for the upcoming summer months.