Except for parts of the northwest Pacific, Indian Ocean and Pacific Ocean hurricanes always begin to develop in troughs located at high enough latitudes for low-level westerly winds to be observed on their equatorial sides. These near-equatorial troughs coincide with axes of maximum sea surface temperature, and in this respect they resemble continental heat troughs. Oceanic near-equatorial troughs follow the march of the sun. Generally, the farther they are from the equator the more often do hurricanes begin to form in them. The meridional rate of trough movement depends on the rate of ocean surface heating. Seas east and equatorward of the continents. Through the spring, continental heating rapidly diminishes the equatorward winds of winter, reducing evaporational cooling of the sea surface and mixed-layer depth. The consequent sea surface temperature rise brings the near-equatorial troughs poleward and starts the hurricane season only. In the height of summer, monsoon winds by increasing evaporational cooling and mixed-layer depth cause sea surface temperatures to fall; the trough is largely over land (heat trough) and hurricanes become rare. In the autumn transition, surface winds are once again light and hurricane frequency attains a second maximum. Seas west of the continents and the open oceans. Through the spring, continental heating helps prolong the equatorward winds of winter over neighboring seas. Elsewhere too, trade winds maintain a deep mixed layer and considerable evaporational cooling. Thus the near-equatorial trough remains too close to the equator for tropical cyclogenesis. However, by midsummer except over the central and southeast Pacific, the trough reaches high enough latitudes for hurricanes to develop, the season starts, and hurricane frequency soon attains a single maximum. Oceanic near-equatorial troughs more than 5° from the equator satisfy most of the prerequisites for hurricane development. Because hurricanes cool the sea surface, time and space intervals between hurricane developments seem to be inversely related.