California’s shaky power grid is on a collision course with an epic drought that’s depleting a major source of supply: hydroelectricity.

The Western heatwave that began Wednesday has the manager of the state’s grid, the California Independent System Operator, warning of potential power shortages through the weekend. Although the organization stopped short of predicting another round of rolling blackouts, it appealed to Californians to conserve energy to get the state through a tough week. The National Weather Service said temperatures are expected to reach 110 degrees Thursday.