Metro suspended operations Sunday night on all routes and lines as a result of hazardous road conditions, the transit agency said.
Metro said deteriorating conditions, including ice formation, have affected its ability to operate safely.
In a later announcement, Metro said bus service would resume Monday morning, but on major roads only. It said delays and increased waiting times should be expected.
It recommended that those who take the bus should use Metrorail if possible. Metrorail will continue normal service until its regular 11 p.m. closing, Metro said. The transit agency said rail service would again be normal on Monday.