Spring is one of the four seasons. In the temperate zones, it is the time of awakening and sprouting nature.
Depending on whether spring prevails in the northern hemisphere or the southern hemisphere, a distinction is made between northern spring and southern spring. Due to the changing position of the sun between the southern and northern tropics, spring repeats itself in every hemisphere in an annual cycle. The spring of one hemisphere always coincides with the autumn of the other.
Spring begins astronomically in the northern hemisphere with the day-and-night equation on March 19 or 20 (in the southern hemisphere accordingly on September 22 or 23); meteorologically and biologically, it is usually scheduled for early March.
Spring ends astronomically on June 21 in the northern hemisphere (summer solstice).
The beginning of spring can either be determined astronomically, i.e. according to the position of the earth towards the sun, phenologically according to the stage of development of the plants or meteorologically. Astronomically, it begins with the spring equinox; (one also speaks of the Equinox or the day and night equation):
In the northern hemisphere earlier on March 20 or 21, in 2011 for the first time for the last time on March 21, then always on March 20 to 2048, then in changing cases on March 19 or March 20.
in the southern hemisphere on September 22 or 23.
With the astronomical beginning of summer at the summer solstice on June 21, spring always ends on the same day.
Spring starts with the first flowering of regionally different plant species.
In the northern hemisphere, this usually occurs in March, April, and May,
in the southern hemisphere, however, in September, October and November.
In Central Europe, therefore, early spring already begins with the first flowers of the snowdrops, but full spring is only reached when the apple trees begin to bloom.
Spring Equinox seen from the Pizzo Vento  site at Fondachelli Fantina, Sicily
This period, in which nature awakens, is also called spring in German.
Spring begins meteorologically
in the northern hemisphere on March 1st,
in the southern hemisphere on September 1st.
Like the three other seasons, summer, autumn and winter, it is (meteorologically speaking) exactly three months long and was determined for statistical reasons. However, no expectations of the weather may be derived from these statistical periods, they are the three calendar months in which the most likely summer, etc. weather is to be expected. This division makes it easier to divide months into “dry”, “hot”, “cold” etc.
Effect on humans
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With increasing light intensity, serotonin and dopamine are released. These provide a generally better feeling and cause a slight euphoria. The desire for a partner is also stronger in most people in spring, caused, among other things, by increased hormone release. However, this has not been scientifically proven. Optical stimuli from lighter clothing probably also play a role.  In contrast to these so-called spring feelings, spring tiredness occurs in some people. This is mainly attributed to the sleep hormone melatonin, which is still strongly present in the blood, but the exact cause is still unclear.
In many cultures there are spring festivals and spring rites. For example, various ecclesiastical moving holidays are derived from the beginning of spring. The Persian or Kurdish New Year and the New Year of the Bahá’í are celebrated, for example, on the Nouruz.
Many spring flowers – especially onion plants – retreat underground after flowering and leave their place to later bloomers. Examples of violets and primroses are known from the garden.