Firefighters working in searing heat struggled to contain the largest wildfire in California this year while state power operators urged people to conserve energy after a huge wildfire in neighboring Oregon disrupted the flow of electricity from three major transmission lines. A large swath of the West baked during the weekend in triple-digit temperatures that were expected to continue into the start of the work week. Managers of California’s power grid issued a five-hour ”flex alert” starting at 4 p.m. Monday and asked consumers to “conserve as much electricity as possible” to avoid outages. California’s largest fire is burning near the Nevada border north of Lake Tahoe and grew by a third on Sunday.