Hurricanes form in the Atlantic and
east Pacific oceans, when the surface
temperature of the ocean is at least
27°C 1 F) over a wide, deep area
and the condition in the atmosphere
are right. Because they are fuelled by
warm water, they lose their strength
over land. They are divided into
categories, with category 1 the least
and category 5 the worst. As well as
the high winds, damage is caused by
hail, heavy rainfall that can cause
mudslides and storm surges, which
cause flooding. In 2005, hurricane
Katrina's storm surge caused more
damage than the winds when it
reached the flood defences at New
Orleans. Elsewhere such storms
are called typhoons and tropical cyclones