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Spring is one of the four conventional temperate seasons, following winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures and customs. When it is spring in the northern hemisphere, it will be autumn in the southern hemisphere. At the spring equinox, days are close to 12 hours long with day length increasing as the season progresses. Spring and "springtime" refer to the season, and also to ideas of rebirth, rejuvenation, renewal, resurrection, and regrowth.
Meteorological reckoning 
Meteorologists generally define four seasons in many climatic areas: spring, summer, autumn (fall) and winter. 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 terms of complete months, in most north temperate zone locations, spring months are March, April and May, although differences exist from country to country. (Summer is June, July, August; autumn is September, October, November; winter is December, January, February). Most south temperate zone locations have opposing seasons with spring in September, October and November. 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.
Astronomical and solar reckoning 
In some regions in the Northern Hemisphere, the astronomical March equinox (varying between 19 and 21 March) is taken to mark the first day of spring, and the Northern solstice (around 21 June) is taken as the first day of summer. In other regions, the equinox is taken as mid-spring.
In South America, the Tupi-Guaraní 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 people, 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).
Other calendar-based reckoning 
According to another tradition in the USA, 2 February, Candlemas, can be regarded as the start of spring if it is mild (see Groundhog Day). The US spring season can also be regarded as beginning on the day after Presidents' Day (the Tuesday after the third Monday in February) and ending on the Friday before Memorial Day weekend (the Friday before the last Monday in May). In South Africa, Australia, and New Zealand, spring begins on 1 September, and has no relation to the vernal equinox. In Ireland spring traditionally starts on 1 February, St Brigid's Day, although Irish meteorologists consider the whole of February to be part of winter.
Ecological reckoning 
The beginning of spring is not always determined by fixed calendar dates. The phenological or ecological definition of spring relates to biological 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. Most ecologists divide the year into six seasons that have no fixed dates. In addition to spring, ecological reckoning identifies an earlier separate prevernal (early or pre-spring) season between the hibernal (winter) and vernal (spring) seasons. This is a time when only the hardiest flowers like the crocus are in bloom, sometimes while there is still some snowcover on the ground.
Natural events 
In spring, the axis of the Earth is increasing its tilt relative to the Sun, and the length of daylight rapidly increases for the relevant hemisphere. The hemisphere begins to warm significantly causing new plant growth to "spring forth," giving the season its name. Snow, if a normal part of winter, begins to melt, and streams swell with runoff. Frosts, if a normal part of winter, become less severe. In climates that have no snow and rare frosts, the air and ground temperatures increase more rapidly. Many flowering plants bloom this time of year, in a long succession sometimes beginning when snow is still on the ground, continuing into early summer. In normally snowless areas "spring" may begin as early as February (Northern Hemisphere) heralded by the blooming of deciduous magnolias, cherries, and quince, or August (Southern Hemisphere) in the same way. Subtropical and tropical areas have climates better described in terms of other seasons, e.g. dry or wet, or monsoonal, or cyclonic. Often the cultures have locally defined names for seasons which have little equivalence to the terms originating in Europe. Many temperate areas have a dry spring, and wet autumn (fall), which brings about flowering in this season more consistent with the need for water as well as warmth. Subarctic areas may not experience "spring" at all until May or even June.
While spring is a result of the warmth caused by the changing orientation of the Earth's axis relative to the Sun, 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.
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.
Cultural events 
Akitu (Sumerian Akiti-šekinku "cutting of barley", Akiti-šununum "sowing of barley", Babylonian rêš-šattim "head of the year") was a spring festival in ancient Mesopotamia. The name is from the Sumerian for "barley", originally marking two festivals celebrating the beginning of each of the two half-years of the Sumerian calendar, marking the sowing of barley in autumn and the cutting of barley in spring, in the month of Nisannu (Aries). In Babylonian religion it came to be dedicated to Marduk's victory over Tiamat.
Spring in Cyprus starts on the 1st March for 3 months. Regarding Kyros Artemis starts 20 of March.
Sham ennisim (Egyptian Arabic: شم النسيم, IPA: [ˈʃæmm enneˈsiːm], from Coptic: Ϭⲱⲙ‘ⲛⲛⲓⲥⲓⲙ shom ennisim) is an Egyptian national holiday marking the beginning of spring. It always falls on the day after the Eastern Christian Easter (following the custom of the largest Christian denomination in the country, the Coptic Orthodox Church). Despite the Christian-related date, the holiday is celebrated by Egyptians regardless of religion.
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 host city of Melbourne. It is also referred to as The race that stops a nation.
Iranian people 
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 of Persian people, such as Azerbaijan, Afghanistan, Kyrgyzstan and Tajikistan, and by Kurdish communities in Turkey and Iraq and elsewhere.
May Day 
1 May is the date of many public holidays. In many countries, May Day is synonymous with International Workers' Day, or Labour Day, which celebrates the social and economic achievements of the labour movement. As a day of celebration the holiday has ancient origins, and it can relate to many customs that have survived into modern times. Many of these customs are due to May Day being a cross-quarter day, meaning that (in the Northern Hemisphere where it is almost exclusively celebrated) it falls approximately halfway between the spring equinox and summer solstice. In the Celtic tradition, this date marked the end of Spring and the beginning of Summer. In line with this, Ireland celebrates St Brigid's Day (1 February) as the first day of Spring.
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 March 22nd and April 25th in Western tradition, and between April 4th and May 8th in Eastern Christianity.
Holi, the festival of colours, celebrated at the end of the winter season, is the most vibrant festival of colours celebrated by Hindus in India. People throw water and apply coloured powders on each other.
Vasant Panchami is celebrated in North India on the fifth day of the Indian month Magh (January–February), the first day of spring. Thai Pongal and Sankranti are celebrated in Tamil Nadu and Andhra Pradesha respectively. (Karnataka, Andhra Pradesh and Tamil Nadu) in mid-January to mark the beginning of the spring season.
In Assam and other North-eastern states of India, Rongali Bihu is celebrated for seven days from April 13 to 19. This is a harvesting festival celebrated by all sections of the community, which distinguishes it from other Indian festivals that are more religious in nature.
Sinhala and Hindu New Year 
Cultural anthropological history of the 'Traditional New Year', which is celebrated in the month of April, goes back to an ancient period in Sri Lankan history. Various beliefs, perhaps those associated with fertility of the harvest, gave birth to many rituals, customs, and ceremonies connected with the New Year. The advent of Buddhism in the 3rd century BC led to a re-interpretation of the existing New Year activities in a Buddhist light. The majority of the people in the country are Buddhists and Hindus, and as such, it is the Buddhist outlook that was predominant in transforming the New Year rites to what they are now.
Vietnamese use the traditional lunar as well as the modern solar calendar. They celebrate Tết (Vietnamese New Year) in late January or early February is also known as the beginning of Spring. The lunar calendar is used mainly to divide the year into seasons for agriculture purposes. In the old days, the celebration used to last the entire month of January of the lunar calendar. Traditionally, firecrackers are used on New Year's Eve, or đêm giao thừa in Vietnamese, to scare away bad spirits and souls.
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- (Portuguese) pt:Calendário tupi-guarani
- Germano Afonso (February 2006). "Mitos e Estações no céu Tupi-Guarani" (in Portuguese). Retrieved 9 October 2010.
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- Michael Allaby (1999). "A Dictionary of Zoology". Retrieved 2012-05-30.
- Anthony Aveni, "May Day: A Collision of Forces," The Book of the Year: A Brief History of Our Seasonal Holidays (Oxford: Oxford University Press, 2004), 79–89.
- Anthony Aveni, "The Easter/Passover Season: Connecting Time's Broken Circle," The Book of the Year: A Brief History of Our Seasonal Holidays (Oxford: Oxford University Press, 2004), 64–78.
- This resurrection is commonly said to have occurred "on the third day after resting for the Sabbath(Friday sundown to Saturday sundown), including the day of crucifixion. (e.g. Luke 24:21 KJV)
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- Word Lore
- Online Etymology Dictionary
- Glossary of Meteorology
- Solstice, Equinox & Cross-Quarter Moments for 2011 and other years, for several timezones
- Earth's Seasons, Equinoxes, Solstices, Perihelion, and Aphelion, 2000–2020 (from the United States Naval Observatory's Astronomical Applications Department)
- Seasons and Seasonal Cusps as Pagan and Religious Holidays (from Archaeoastronomy)
- What day does spring start? (BBC, UK News Magazine)