Tens of thousands of Oregon homes and businesses were still without electricity early Tuesday, as the National Weather Service warned of more challenging conditions to come. Portland Public Schools, Salem-Keizer, Eugene 4J and many other districts canceled classes on Tuesday. Portland warned that its sewer system is strained, and the MAX service remains shut down. At least four deaths may be linked to the weather. The National Weather Service is forecasting freezing rain across northwest Oregon and southwest Washington starting late Tuesday morning. State agencies are warning Oregonians to stay off roads and prepare for additional tree damage and power outages.