Mayor John DeStefano Jr. announced a state of emergency in New Haven Sunday afternoon, issuing mandatory evacuations for areas with the highest risk of flooding.

DeStefano said in a statement that New Haven public schools will close Monday and Tuesday in anticipation of Hurricane Sandy, and that residents should prepare for extended power outages. Evacuations of flood-prone regions will commence at 8:30 a.m. Monday, with the order remaining in place until the noon high tide on Tuesday.

“Residents should take this storm very seriously,” DeStefano said. “The city is preparing for storm surges in excess of Hurricane Irene.”

Residents of evacuation areas are due to be informed today of the order by the Fire Department, Police Department and Livable City Initiative, with Career High School serving as an emergency shelter.

DeStefano warned residents to be wary while driving in case of the temporary absence of traffic signs. Transportation by train to and from the city will halt after 7 p.m. when the Metro-North lines close.

Vice President Linda Lorimer said in an email to the Yale community Sunday afternoon that the University will be consulting closely with the New Haven officials to plan for the storm. She said Yale will issue a full update about its storm response no later than 6:30 p.m.