MARCH 20 - First Day of Spring (Equinox)

MARCH 20 - First Day of Spring (Equinox)

         

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. Early annuals bloom in the spring. 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.

Definition

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. In the vast majority of Northern Hemisphere locations, spring occurs during the months of March, April and May. (Summer is June, July, August; Autumn is September, October, November; Winter is December, January, February.) The vast majority of Southern Hemisphere locations will have opposing seasons with spring in September, October and November.

Astronomically, the vernal equinox (usually March 20 in the Northern Hemisphere, and September 22 in the Southern Hemisphere), should be the middle of spring (based on the angle of the sun and insolation) and the summer solstice (usually June 21 in the Northern Hemisphere and December 21 in the Southern Hemisphere) should be mid-summer (because the sun is at its highest) but daytime temperatures lag behind insolation by several weeks because the earth and sea have thermal latency and take time to warm up. Some cultures, such as those who devised the Celtic and East Asian calendars, call the spring equinox mid-spring, but others (especially in the USA and England) regard it as the "first day of spring". For most temperate regions, signs of spring appear long before the middle of March, but the folklore of March 21 being the "first day of spring" persists, and June 21 as the "first day of summer" is common in the USA. In South Africa, Australia and New Zealand, spring begins on September 1, and has no relation to the vernal equinox.

According to the Celtic tradition, which is based solely on daylight and the strength of the noon sun, spring begins in early February (near Imbolc or Candlemas) and continues until early May (Beltane).

The phenological definition of spring relates to indicators, the blossoming of a range of plant species, and the activities of animals, or the special smell of soil that has reached the temperature for micro flora to flourish. The first swallow to arrive or the flowering of lilac may be the indicator of spring. It therefore varies according to the climate and according to the specific weather of a particular year.

Spring is often a very rainy and muddy season, especially in the Northeast US


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