(CNN) -- Weather conditions are expected to give a boost to search efforts in rural Washington, where a landslide killed 30 people last month.
Thirteen people are still missing, a spokeswoman with the Snohomish County Emergency Operations Center said Sunday.
"Overnight rain caused water levels to increase up to half a foot in some areas, but warmer temperatures and drier conditions are projected for the next couple of weeks, which should assist search efforts," Meg Matthews said.
She added that Secretary of Homeland Security Jeh Johnson and Federal Emergency Management Agency Administrator Craig Fugate joined Washington Gov. Jay Inslee to survey the damage and to thank responders.
A square mile of wet earth and rock rushed into the outskirts of the town of Oso in the North Cascade Mountains on March 22. The slide came from a rain-saturated hillside along the north fork of the Stillaguamish River.
Bodies were found in the debris, which is 70 feet thick in some places. Crews have been searching for people listed as missing.
"Today, hundreds of searchers continued the painstaking work of combing the site and excavating debris," said Matthews.
CNN's Joseph Netto contributed to this report.