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- Author: JCVdude
Allegory of Spring by Jerzy Siemiginowski, 1680s]]
Astronomically, the vernal equinox marks the first day of spring, (currently around the 20th or 21st of March in the Northern Hemisphere, and 22nd or 23rd September in the Southern Hemisphere), whereas the summer solstice marks the first day of summer (usually 21 June in the Northern Hemisphere and 21 December in the Southern Hemisphere). In South Africa, Australia and New Zealand, spring begins on 1 September, and has no relation to the vernal equinox. In Ireland spring traditionally started on 1 February.
The summer solstice is generally not the warmest day nor is the winter solstice the coldest day because temperatures lag by several weeks because the earth and sea have thermal latency and take time to warm up and cool down, a.k.a. hysteresis effect.
In South America, the Tupi-Guarani calendar, from the former inhabitants of what is presently Brazil, Northern Argentina and Paraguay, counted 365 days, plus a fourth part of a day, needing no extra day every four years. The beginning of the solar year was marked by the rising of the M25 Constellation in the horizon, which occurs between June 5 and June 11 in this part of the world. For these native peoples, the four seasons were clearly identified by the solstices and equinoxes. The trajectory of the Sun throughout the year was divided into "The New Age" (Ara Pyau) and "The Old Age" (Ara Ymã). Ara Pyau was spring and summer, and Ara Ymã was autumn and winter. This calendar, which had no graphed or written form, marked activities such as hunting, fishing, planting, harvesting and religious rituals.
In East Asian Solar term, spring begins on 4 February and ends on 5 May. Similarly, 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).
Swedish meteorologists define the beginning of spring as the first occasion on which the average daytime temperature exceeds zero degrees Celsius for seven consecutive days, thus the date varies with latitude and elevation.
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. It therefore varies according to the climate and according to the specific weather of a particular year.
While spring is a result of the warmth caused by the turning of the Earth's axis, the weather in many parts of the world is overlain by events which appear very erratic taken on a year-to-year basis. The rainfall in spring (or any season) follows trends more related to longer cycles or events created by ocean currents and ocean temperatures. Good and well-researched examples are the El Niño effect and the Southern Oscillation Index.
Unstable weather may more often occur during spring, when warm air begins on occasions to invade from lower latitudes, while cold air is still pushing on occasions from the Polar regions. Flooding is also most common in and near mountainous areas during this time of year because of snowmelt, accelerated by warm rains. In the United States, Tornado Alley is most active this time of year, especially since the Rocky Mountains prevent the surging hot and cold air masses from spreading eastward and instead force them into direct conflict. Besides tornadoes, supercell thunderstorms can also produce dangerously large hail and very high winds, for which a severe thunderstorm warning or tornado warning is usually issued. Even more so than in winter, the jet streams play an important role in unstable and severe weather in the springtime in the Northern Hemisphere.
In recent decades season creep has been observed, which means that many phenological signs of spring are occurring earlier in many regions by a couple of days per decade.
Spring is seen as a time of growth, renewal, of new life (both plant and animal) being born. The term is also used more generally as a metaphor for the start of better times, as in the Prague Spring. Spring in the Southern Hemisphere is different in several significant ways to that of the Northern Hemisphere. This is because: there is no land bridge between Southern Hemisphere countries and the Antarctic zone capable of bringing in cold air without the temperature-mitigating effects of extensive tracts of water; the vastly greater amount of ocean in the Southern Hemisphere at all latitudes; at this time in Earth's geologic history the Earth has an orbit which brings it in closer to the Southern Hemisphere for its warmer seasons; there is a circumpolar flow of air (the roaring 40s and 50s) uninterrupted by large land masses; no equivalent jet streams; and the peculiarities of the reversing ocean currents in the Pacific.
The annual Spring Racing Carnival of thoroughbred horse racing events is held in Melbourne in October and November, with large crowds attending. The Melbourne Cup, held on the first Tuesday of November, is Australia's premier horse race and is recognised as a public holiday in the state of Victoria and the territory of the nation's capital, Australian Capital Territory. It is also referred to as The race that stops a nation.
The first day of spring (celebrated on the day of the astronomical vernal equinox, which usually occurs on 21 March or the previous or following day depending on where it is observed) is the beginning of the new year, Nowruz, in the Iranian calendar. Nowruz (also Naw-Rúz, Norooz, Newroz, Navroj, and many other variants) which means "New Day" in Persian language, marks an important traditional holiday festival celebrated in Iran as well as in many other countries with a significant population from one of various Iranian peoples, such as Azerbaijan, Afghanistan and Tajikistan, and by Kurdish communities in Turkey and Iraq and elsewhere.
Easter is the most important religious feast in the Christian liturgical year. Christians believe that Jesus was resurrected from the dead on the "third day" (two days after his crucifixion), and celebrate this resurrection on Easter Day, two days after Good Friday. The date of Easter varies between 22 March and 25 April in Western tradition, and between 4 April and 8 May in Eastern Christianity.
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