DUBAI, April 17 -- Heavy rains lashed the United Arab Emirates on Tuesday, flooding out portions of major highways and leaving vehicles abandoned on roadways across Dubai. Meanwhile, the death toll in separate heavy flooding in neighboring Oman rose to 18 with others still missing as the sultanate prepared for the storm.

The rains began overnight, leaving massive ponds on streets as whipping winds disrupted flights at Dubai International Airport, the world's busiest for international travel and the home of the long-haul carrier Emirates.

Police and emergency personnel drove slowly through the flooded streets, their emergency lights flashing across the darkened morning. Lightning flashed across the sky, occasionally touching the tip of the...