Prime Minister's Benjamin Netanyahu's counterterrorism office says there's a "very high concrete threat" of attacks and recommends Israelis leave the area immediately and those planning on visiting change plans.
It's the highest level of warning Israel issues.
Southern Sinai, with its pristine beaches and Red Sea coral reefs, has traditionally been a popular tourist destination for Israelis.
But tourism there has declined since 2013, when the Egyptian military overthrew an elected Islamist president and an Islamic insurgency based in northern Sinai intensified.
Yesterday's travel warning is one of those Israel issues occasionally based on intelligence reports.