|Northern temperate zone|
|Astronomical season||21 June – 23 September|
|Meteorological season||1 June – 31 August|
|Solar (Celtic) season||1 May – 31 July|
|Southern temperate zone|
|Astronomical season||22 December – 21 March|
|Meteorological season||1 December – 28/29 February|
|Solar (Celtic) season||1 November – 31 January|
| Summer |
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Summer is the hottest of the four temperate seasons, falling after spring and before autumn. At or around the summer solstice (about 3 days before Midsummer Day), the earliest sunrise and latest sunset occurs, the days are longest and the nights are shortest, with day length decreasing as the season progresses after the solstice. The date of the beginning of summer varies according to climate, tradition, and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice versa.
From an astronomical view, the equinoxes and solstices would be the middle of the respective seasons,but sometimes astronomical summer is defined as starting at the solstice, the time of maximal insolation, often identified with the 21st day of June or December. A variable seasonal lag means that the meteorological centre of the season, which is based on average temperature patterns, occurs several weeks after the time of maximal insolation. The meteorological convention is to define summer as comprising the months of June, July, and August in the northern hemisphere and the months of December, January, and February in the southern hemisphere. Under meteorological definitions, all seasons are arbitrarily set to start at the beginning of a calendar month and end at the end of a month. This meteorological definition of summer also aligns with the commonly viewed notion of summer as the season with the longest (and warmest) days of the year, in which daylight predominates. The meteorological reckoning of seasons is used in Australia, Austria, Denmark, Russia and Japan. It is also used by many in the United Kingdom and in Canada. In Ireland, the summer months according to the national meteorological service, Met Éireann, are June, July and August. However, according to the Irish Calendar, summer begins on 1 May and ends on 1 August. School textbooks in Ireland follow the cultural norm of summer commencing on 1 May rather than the meteorological definition of 1 June.
Days continue to lengthen from equinox to solstice and summer days progressively shorten after the solstice, so meteorological summer encompasses the build-up to the longest day and a diminishing thereafter, with summer having many more hours of daylight than spring. Reckoning by hours of daylight alone, summer solstice marks the midpoint, not the beginning, of the seasons. Midsummer takes place over the shortest night of the year, which is the summer solstice, or on a nearby date that varies with tradition.
Where a seasonal lag of half a season or more is common, reckoning based on astronomical markers is shifted half a season.By this method, in North America, summer is the period from the summer solstice (usually 20 or 21 June in the Northern Hemisphere) to the autumn equinox.
Reckoning by cultural festivals, the summer season in the United States is traditionally regarded as beginning on Memorial Day weekend (the last weekend in May) and ending on Labor Day (the first Monday in September), more closely in line with the meteorological definition for the parts of the country that have four-season weather. The similar Canadian tradition starts summer on Victoria Day one week prior (although summer conditions vary widely across Canada's expansive territory) and ends, as in the United States, on Labour Day.
In Chinese astronomy, summer starts on or around 5 May, with the jiéqì (solar term) known as lìxià (立夏), i.e. "establishment of summer", and it ends on or around 6 August.
In southern and southeast Asia, where the monsoon occurs, summer is more generally defined as lasting from March, April, May and June, the warmest time of the year, ending with the onset of the monsoon rains.[ citation needed ]
Because the temperature lag is shorter in the oceanic temperate southern hemisphere,most countries in this region use the meteorological definition with summer starting on 1 December and ending on the last day of February.
Summer is traditionally associated with hot or warm weather. In Mediterranean climates, it is also associated with dry weather, while in other places (particularly in Eastern Asia because of the monsoon) it is associated with rainy weather. The wet season is the main period of vegetation growth within the savanna climate regime.Where the wet season is associated with a seasonal shift in the prevailing winds, it is known as a monsoon.
In the northern Atlantic Ocean, a distinct tropical cyclone season occurs from 1 June to 30 November.The statistical peak of the Atlantic hurricane season is 10 September. The Northeast Pacific Ocean has a broader period of activity, but in a similar timeframe to the Atlantic. The Northwest Pacific sees tropical cyclones year-round, with a minimum in February and March and a peak in early September. In the North Indian basin, storms are most common from April to December, with peaks in May and November. In the Southern Hemisphere, the tropical cyclone season runs from the start of November until the end of April with peaks in mid-February to early March.
Thunderstorm season in the United States and Canada runs in the spring through summer but sometimes can run as late as October or even November in the fall. These storms can produce hail, strong winds and tornadoes, usually during the afternoon and evening.
Schools and universities typically have a summer break to take advantage of the warmer weather and longer days. In almost all countries, children are out of school during this time of year for summer break, although dates vary. In the United States, public schools usually end in late May in Memorial Day weekend, while colleges finish in early May. Public school traditionally resumes near Labor Day, while higher institutions often resume in mid-August. In England and Wales, school ends in mid-July and resumes again in early September; in Scotland, the summer holiday begins in late June and ends in mid-to late-August. Similarly, in Canada the summer holiday starts on the last or second-last Friday in June and ends in late August or on the first Tuesday of September, with the exception of when that date falls before Labour Day, in which case, ends on the second Tuesday of the month. In Russia the summer holiday begins at the end of May and ends on 31 August.
In the Southern Hemisphere, school summer holiday dates include the major holidays of Christmas and New Year's Day. School summer holidays in Australia, New Zealand and South Africa begin in early December and end in early February, with dates varying between states. In South Africa, the new school year usually starts during the second week of January, thus aligning the academic year with the Calendar year. In India, school ends in late April and resumes in early or mid-June. In Cameroon and Nigeria, schools usually finish for summer vacation in mid-July and resume in the later weeks of September or the first week of October.
A wide range of public holidays fall during summer, including:
People generally take advantage of the high temperatures by spending more time outdoors during summer. Activities such as travelling to the beach and picnics occur during the summer months. Sports such as soccer, basketball, football, volleyball, skateboarding, baseball, softball, cricket, tennis and golf are played. Water sports also occur. These include water skiing, wakeboarding, swimming, surfing, tubing and water polo. The modern Olympics have been held during the summer months every four years since 1896. However, the 2000 Summer Olympics, in Sydney, were held during the Spring and the 2016 Summer Olympics, in Rio de Janeiro, were held in Winter.
Summer is normally a low point in television viewing, and television schedules generally reflect this by not scheduling new episodes of their most popular shows between the end of May sweeps and the beginning of the television season in September, instead scheduling low-cost reality television shows and burning off commitments to already-cancelled series. There is an exception to this with children's television. Many television shows made for children and are popular with children are released during the summer months, especially on children's cable channels such as the Disney Channel in the United States, as children are off school. Disney Channel, for example, ends its pre-school programming earlier in the day for older school-age children in the summer months while it reverts to the original scheduling as the new school year begins. Conversely, the music and film industries generally experience higher returns during the summer than other times of the year and market their summer hits accordingly. Summer is most popular for animated movies to be released theatrically in movie theaters.[ citation needed ]
With most school-age children and college students (except those attending summer school and summer camp) on summer vacation during the summer months, especially in the United States, travel and vacationing traditionally peak during the summer, with the volume of travel in a typical summer weekend rivalled only by Thanksgiving. Teenagers and college students often take summer jobs in industries that cater to recreation. Business activity for the recreation, tourism, restaurant, and retail industries peaks during the summer months as well as the holiday season.
Autumn, also known as fall in North American English, is one of the four temperate seasons. Outside the tropics, autumn marks the transition from summer to winter, in September or March, when the duration of daylight becomes noticeably shorter and the temperature cools considerably. Day length decreases and night length increases as the season progresses until the Winter Solstice in December and June. One of its main features in temperate climates is the shedding of leaves from deciduous trees.
Winter is the coldest season of the year in polar and temperate zones; it does not occur in most of the tropical zone. It occurs after autumn and before spring in each year. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value. The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice. The earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit.
Spring, also known as springtime, is one of the four temperate seasons, succeeding 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 is autumn in the Southern Hemisphere and vice versa. At the spring equinox, days and nights are approximately twelve hours long, with daytime length increasing and nighttime length decreasing as the season progresses.
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere. The formation process of a low-pressure area is known as cyclogenesis. Within the field of meteorology, atmospheric divergence aloft occurs in two areas. The first area is on the east side of upper troughs, which form half of a Rossby wave within the Westerlies. A second area of wind divergence aloft occurs ahead of embedded shortwave troughs, which are of smaller wavelength. Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity.
Seasonal lag is the phenomenon whereby the date of maximum average air temperature at a geographical location on a planet is delayed until some time after the date of maximum insolation. This also applies to the minimum temperature being delayed until some time after the date of minimum insolation.
The 2006 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean.
The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and northern hemispheres.
The 1996 North Indian Ocean cyclone season featured several deadly tropical cyclones, with over 2,000 people killed during the year. The India Meteorological Department (IMD) – the Regional Specialized Meteorological Center for the northern Indian Ocean as recognized by the World Meteorological Organization – issued warnings for nine tropical cyclones in the region. Storms were also tracked on an unofficial basis by the American-based Joint Typhoon Warning Center, which observed one additional storm. The basin is split between the Bay of Bengal off the east coast of India and the Arabian Sea off the west coast. During the year, the activity was affected by the monsoon season, with most storms forming in June or after October.
The 1981 North Indian Ocean cyclone season was part of the annual cycle of tropical cyclone formation. The season has no official bounds but cyclones tend to form between April and December. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. There are two main seas in the North Indian Ocean—the Bay of Bengal to the east of the Indian subcontinent and the Arabian Sea to the west of India. The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center (JTWC) releases unofficial advisories. An average of five tropical cyclones form in the North Indian Ocean every season with peaks in May and November. Cyclones occurring between the meridians 45°E and 100°E are included in the season by the IMD.
An upper tropospheric cyclonic vortex is a vortex, or a circulation with a definable center, that usually moves slowly from east-northeast to west-southwest and is prevalent across Northern Hemisphere's warm season. Its circulations generally do not extend below 6,080 metres (19,950 ft) in altitude, as it is an example of a cold-core low. A weak inverted wave in the easterlies is generally found beneath it, and it may also be associated with broad areas of high-level clouds. Downward development results in an increase of cumulus clouds and the appearance of circulation at ground level. In rare cases, a warm-core cyclone can develop in its associated convective activity, resulting in a tropical cyclone and a weakening and southwest movement of the nearby upper tropospheric cyclonic vortex. Symbiotic relationships can exist between tropical cyclones and the upper level lows in their wake, with the two systems occasionally leading to their mutual strengthening. When they move over land during the warm season, an increase in monsoon rains occurs.
The 1996–97 South Pacific cyclone season was one of the most active and longest South Pacific tropical cyclone seasons on record, with 12 tropical cyclones occurring within the South Pacific basin between 160°E and 120°W. The season officially ran from November 1, 1996 - April 30, 1997, however, the season ended later than normal with three systems monitored after the official end of the season. The strongest tropical cyclone of the season was Cyclone Gavin which had a minimum pressure of 925 hPa (27.32 inHg). After the season had ended 4 tropical cyclone names were retired from the naming lists, after the cyclones had caused significant impacts to South Pacific islands.
The 1986–87 South Pacific cyclone season was an event in the annual cycle of tropical cyclone formation. A total of 13 tropical cyclones developed during the season.
The 1990–91 Australian region cyclone season was a slightly below average cyclone season, with ten tropical cyclones occurring within the region between 90°E and 160°E. The season officially ran from November 1, 1990, to April 30, 1991, with the first disturbance of the season forming on 10 December and the last disturbance moving out of the region during 11 May. Six people were killed by Cyclone Joy when it made landfall on Australia. During the season, tropical cyclones were monitored by the Australian Bureau of Meteorology, who ran Tropical Cyclone Warning Centers (TCWC) in Perth, Darwin, and Brisbane. The United States Joint Typhoon Warning Center (JTWC) and Papua New Guinea National Weather Service also monitored systems within the basin during the season. The JTWC designated systems with a number and either a S or a P suffix depending on which side of 135E. The Bureau of Meteorology and Papua New Guinea national Weather Service both used the Australian Tropical Cyclone Intensity Scale, and estimated windspeeds over a ten-minute period, while the JTWC estimated sustained winds over a one-minute period and are comparable to the Saffir–Simpson Hurricane Scale.
The 1989–90 Australian region cyclone season was an above average tropical cyclone season. It was also an event in the ongoing cycle of tropical cyclone formation. It ran from 1 November 1989 to 30 April 1990. The regional tropical cyclone operational plan also defines a tropical cyclone year separately from a tropical cyclone season, and the "tropical cyclone year" ran from 1 July 1989 to 30 June 1990.
A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations, and as such there are a number of both modern and historical cultures whose number of seasons vary.
During 2010, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 111 tropical cyclones had formed this year to date. 64 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC).
During 2005, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 141 systems formed with 94 of these developing further and were named by the responsible warning centre. The strongest tropical cyclone of the year was Hurricane Wilma, which was estimated to have a minimum barometric pressure of 882 hPa (26.05 inHg).
Throughout 2006, 133 tropical cyclones formed in seven bodies of water known as tropical cyclone basins. Of these, 80 have been named, including two tropical cyclones in the South Atlantic Ocean, and a tropical cyclone in the Mediterranean Sea, by various weather agencies when they attained maximum sustained winds of 65 km/h (40 mph). The strongest storms of the year were Typhoon Yagi in the Western Pacific, and Cyclone Glenda of the Australian region. The deadliest and costliest storms of the year were a series of five typhoons that struck the Philippines; Chanchu, Bilis, Saomai, Xangsane, and Durian, with most of the damage being caused by Durian of November.
The 1979–80 Australian region cyclone season was an above average tropical cyclone season.
The 2014 North Indian Ocean cyclone season was an event in the annual cycle of tropical cyclone formation. The season included two very severe cyclonic storms, both in October, and one other named cyclonic storm, classified according to the tropical cyclone intensity scale of the India Meteorological Department. Cyclone Hudhud is estimated to have caused US$3.58 billion in damage across eastern India, and more than 120 deaths.
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