This article is from the Storms FAQ, by Chris Landsea email@example.com with numerous contributions by others.
Hurricanes form both in the Atlantic basin (i.e. the Atlantic
Ocean, Gulf of Mexico and Caribbean Sea) to the east of the
continental U.S. and in the Northeast Pacific basin to the
west of the U.S. However, the ones in the Northeast Pacific
almost never hit the U.S., while the ones in the Atlantic basin
strike the U.S. mainland just less than twice a year on average.
There are two main reasons. The first is that hurricanes tend
to move toward the west-northwest after they form in the tropical
and subtropical latitudes. In the Atlantic, such a motion often
brings the hurricane into the vicinity of the U.S. east coast. In
the Northeast Pacific, a west-northwest track takes those hurricanes
farther off-shore, well away from the U.S. west coast. In addition
to the general track, a second factor is the difference in water
temperatures along the U.S. east and west coasts. Along the U.S.
east coast, the Gulf Stream provides a source of warm (> 80 F or
26.5 C) waters to help maintain the hurricane. However, along the
U.S. west coast, the ocean temperatures rarely get above the lower
70s, even in the midst of summer. Such relatively cool temperatures
are not energetic enough to sustain a hurricane's strength. So
for the occasional Northeast Pacific hurricane that does track
back toward the U.S. west coast, the cooler waters can quickly
reduce the strength of the storm.