It is important to note that whether a storm is called a cyclone, a hurricane or a tropical storm mostly depends on where the storm forms. According to the Hurricane Center, tropical cyclones are called hurricanes in the Western Hemisphere and typhoons in the Eastern Hemisphere, as a general rule. To distinguish a hurricane from a tropical storm, assess the storm's power. Hurricanes are the more powerful of the two.
Clouds and precipitation generally come before a storm -- the hurricane is no different -- but neither must be present for the storm to form. One thing the storm does need to form is warm ocean water. The water must be at least 26 degrees Celsius, or 78 degrees Fahrenheit, for a cyclone to begin to develop. The natural evaporation process forms clouds over the ocean. If these clouds form where a naturally occurring area of low atmospheric pressure is present, then it draws them in. From here, the earth's rotation causes these clouds to rotate, and a storm can potentially develop.
An approaching cyclone may not give any physical signs until it is very close. The first observable changes will be in the ocean, where the swell on the ocean's surface rises and waves become more frequent. Two days before a cyclone makes landfall, there still may be no observable signs to those inland. The first signs do appear some 36 hours before a cyclone makes landfall. At this time, the beginnings of the storm begin to show on the horizon. The barometer falls, but there may be no precipitation yet. On the coasts, waves start coming in every seven seconds and the ocean swell has increased to 13 feet.
When the storm is less than 36 hours from landfall, wind and rain begin in earnest, growing gradually more powerful. Wind gusts can reach more than 100 mph. The rain falls almost horizontally because of the powerful winds. There will be lightning and flying debris. Depending upon how far inland you live, there may be flooding in low-lying areas as well.