USGC has reported that the cleanup operations, particularly the skimmers and burn operations have benefited greatly from the good weather. The obvious effect is the current efforts at containment and stopping the flow would be halted. The containment would be seriously compromised. Surveillance would be reduced, and it would become more difficult to track the spill.
A USGC topo map shows Mount St. Alban in DC, on which the Washington cathedral sits, is regarded as the highest point in DC. At that point, the elevation is 377 feet.