Summer

From an astronomical view, the equinoxes and solstices would be the middle of the respective seasons,[1][2] 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. By solar reckoning, summer instead starts on May Day and the summer solstice is Midsummer. 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.[3]

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.[4][5] 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.[4] 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 countries including Australia, New Zealand, Austria, Denmark, Russia and Japan. It is also used by many people in the United Kingdom and Canada. In Ireland, the summer months according to the national meteorological service, Met Éireann, are June, July and August. By the Irish calendar, summer begins on 1 May (Beltane) and ends on 31 July (Lughnasadh).[6]

In the middle of summer, the sun can appear even at midnight in the northern hemisphere. Photo of midnight sun in Inari, Finland.

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.[7] 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.[8][9][10]

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 some Southern Hemisphere countries such as Brazil, Argentina, South Africa, Australia and New Zealand, summer is associated with the Christmas and New Year holidays. Many families take extended holidays for two or three weeks or longer during summer.

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.

Because the temperature lag is shorter in the oceanic temperate southern hemisphere,[11] most countries in this region use the meteorological definition with summer starting on 1 December and ending on the last day of February.[12][13]

Wet season thunderstorm at night in Darwin, Northern Territory, Australia.

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.[14] Where the wet season is associated with a seasonal shift in the prevailing winds, it is known as a monsoon.[15]

Image of Hurricane Lester from late August 1992.

In the northern Atlantic Ocean, a distinct tropical cyclone season occurs from 1 June to 30 November.[16] 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.[17] 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.[16] 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.[16][18]

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.

Summer is usually the season of travel, swimming, summer vacation for many people, and also the season for fruits and plants to fully develop.

Hotels and tourists along the Atlantic Ocean shoreline in Myrtle Beach, South Carolina in summer

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 including cricket, association football (soccer), horse racing, basketball, American football, volleyball, skateboarding, baseball, softball, 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. The 2000 Summer Olympics, in Sydney, were held in spring and the 2016 Summer Olympics, in Rio de Janeiro, were held in winter.

In the United States, many television shows made for children are released during the summer, as children are off school.

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 popular for animated movies to be released theatrically in movie theaters.

With many schools closed, especially in Western countries, travel and vacationing tend to peak during the summer. Teenagers and university students often take summer jobs, and business activity for the recreation, tourism, restaurant, and retail industries reach their peak.

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  Children cycling during summer
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  Barefoot skiing
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  Fig trees bear fruit when summer is near
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  Using a handheld fan in summer

• Summer Olympic Games
• Summer War