Summer. Summer is the hottest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, the earliest sunrise and latest sunset occurs, daylight hours are longest and dark hours 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. Further information: Meteorological seasons 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. 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. 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 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. 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 to the autumn equinox. Reckoning by cultural festivals, the summer season in the United States is traditionally regarded as beginning on Memorial Day weekend and ending on Labor Day, 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 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 Australia and New Zealand, summer begins on 1 December and ends on 28 February. 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, most countries in this region use the meteorological definition with summer starting on 1 December and ending on the last day of February. See also: Hail, Tropical cyclone, and Wet season Summer is traditionally associated with hot or warm weather. In Mediterranean climates, it is also associated with dry weather, while in other places 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.