The first seven miles of the Intercounty Connector will open early next year.
Almost 95 percent of the work on the first section is complete, ICC spokesman Ray Feldman said, but much of the remaining work, such as paving, requires dry weather and higher temperatures.
Officials had hoped to open the first segment of the nearly 19-mile highway by late 2010 or early 2011.
The first segment runs between Interstate 270 in Gaithersburg, Md., and Georgia Avenue in Silver Spring, Md. The planned six-lane highway will eventually connect Montgomery and Prince George's counties.