Spring marks the transition from winter into summer.Its days are nearly twelve hours long with increasing day length,as it occurs near the time of an equinox.Annuals bloom in the spring.In the Northern Hemisphere,holidays such as Easter and Earth Day occur during the spring,which runs from March into June.In the Southern Hemisphere,holidays such as Rosh Hashanna and Yom Kippur occur during the spring,which runs from September into December.Also,the tropical cyclone season begins during the late spring in both hemispheres,though it is more delayed in the north Atlantic Ocean than the other ocean basins.
Autumn (also known as Fall in North American English) is one of the four temperate seasons.Autumn marks the transition from summer into winter,usually in late March (southern hemisphere) or late September (northern hemisphere) when the arrival of night becomes noticeably earlier.In theory,astronomically,the equinoxes ought to be the middle of the respective seasons,but temperature lag (caused by the thermal latency of the ground and sea) means that seasons appear later than dates calculated from a purely astronomical perspective.The actual lag varies with region,so some cultures regard the autumnal equinox as "mid-autumn" whilst other treat it as the start of autumn.