High Quality Content by WIKIPEDIA articles! Spring is one of the four temperate seasons, the transition period between winter and summer. Its days are close to twelve hours long with increasing day length, as it occurs near the time of an equinox. In the Northern Hemisphere, spring runs from March into May, and in the Southern Hemisphere it runs from September into November. Spring is also the tropical cyclone season in both hemispheres, although it is more delayed in the north Atlantic Ocean than the other ocean basins. Meteorologists generally define four seasons in many climatic areas, winter, spring, summer and autumn (or fall). These are demarcated by the values of their average temperatures on a monthly basis, with each season lasting three months. The three warmest months are by definition summer, the three coldest months are winter, and the intervening gaps are spring and autumn. Spring, when defined in this manner, can start on different dates in different regions.