Consider this your two-month warning: On June 1, U.S. citizens returning from Canada and Mexico by land or sea will need a passport or government-issued border-crossing card to do so. Travelers may also use military ID or enhanced-technology driver's licenses, which are available in Washington, New York, Vermont, and Michigan. Previously, Americans could cross back into the U.S. with a birth certificate or a regular driver's license. The government is worried that many people don't realize the rules will take effect so soon. As Homeland Security Secretary Janet Napolitano told USA Today, "So many people live on the border and are used to crossing back and forth informally," which has given rise to fears of confusion and disruptions to routine traffic across the borders when the rules change. The State Department is bracing for a significant spike in passport applications, so travelers in need of new documentation should plan accordingly. Currently, routine applications should be completed in four to six weeks, but as we saw a few years ago, wait times can grow if passport offices are overwhelmed. Avoid the risk and get your application in early.