Winter is thecoldest and darkestseason of the year intemperate andpolar climates. It occurs afterautumn and beforespring. Thetilt of Earth's axis causes seasons; winter occurs when ahemisphere is oriented away from theSun. Different cultures define different dates as the start of winter, and some use a definition based on weather.
When it is winter in theNorthern Hemisphere, it issummer in theSouthern Hemisphere, and vice versa. Winter typically bringsprecipitation that, depending on a region'sclimate, is mainlyrain orsnow. The moment ofwinter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value; that is, the Sun is at its farthest below the horizon as measured from the pole. The day on which this occurs has the shortest day and the longest night, withday length increasing andnight 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 and depend on latitude. They differ due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit (see:earliest and latest sunrise and sunset).
Etymology
The English wordwinter comes from theProto-Germanic noun*wintru-, whose origin is unclear. Several proposals exist, a commonly mentioned one connecting it to theProto-Indo-European root*wed- 'water' or a nasal infix variant*wend-.[1]
The tilt of the Earth's axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23.44° to the plane of its orbit, causing different latitudes to directly face the Sun as the Earth moves through its orbit. This variation brings about seasons. When it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun. From the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun.
During winter in either hemisphere, the lower altitude of the Sun causes the sunlight to hit the Earth at an oblique angle. Thus a lower amount ofsolar radiation strikes the Earth per unit of surface area. Furthermore, the light must travel a longer distance through the atmosphere, allowing the atmosphere to dissipate more heat. Compared with these effects, the effect of the changes in the distance of the Earth from the Sun (due to the Earth's elliptical orbit) is negligible.
The manifestation of the meteorological winter (freezing temperatures) in the northerly snow-prone latitudes is highly variable, depending on elevation, position versus marine winds, and the amount of precipitation. For instance, withinCanada (a country of cold winters),Winnipeg, on theGreat Plains (a long way from the ocean), has a January high of −11.3 °C (11.7 °F) and a low of −21.4 °C (−6.5 °F).[2]
In comparison,Vancouver, on the west coast (with a marine influence from moderating Pacific winds), has a January low of 1.4 °C (34.5 °F), with days well above freezing, at 6.9 °C (44.4 °F).[3] Both places are at 49°N latitude and in the same western half of the continent. A similar but less extreme effect is found in Europe: despite their northerly latitude, the British Isles have no non-mountain weather stations with a below-freezing mean January temperature.[4]
Meteorological reckoning is the method of measuring the winter season used bymeteorologists based on "sensible weather patterns" for record keeping purposes,[5] so the start of meteorological winter varies with latitude.[6] Winter is often defined by meteorologists to be the three calendar months with the lowest average temperatures. This corresponds to the months of December, January and February in theNorthern Hemisphere, and June, July and August in theSouthern Hemisphere.
The coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Nighttime predominates in the winter season, and in some regions, winter has the highest rate ofprecipitation as well as prolonged dampness because of permanent snow cover or high precipitation rates coupled with low temperatures, precluding evaporation.Blizzards often develop and cause many transportation delays.Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °C (−40 °F) due to air with slightly higher moisture from above mixing with colder, surface-based air.[7] They are made of simple hexagonal ice crystals.[8]
TheSwedish Meteorological Institute (SMHI) definesthermal winter as when the daily mean temperatures are below 0 °C (32 °F) for five consecutive days.[9] According to the SMHI, winter in Scandinavia is more pronounced when Atlantic low-pressure systems take more southerly and northerly routes, leaving the path open for high-pressure systems to come in and cold temperatures to occur. As a result, the coldest January on record in Stockholm, in 1987, was also the sunniest.[10][11]
Accumulations of snow and ice are commonly associated with winter in the Northern Hemisphere, due to the large land masses there. In the Southern Hemisphere, the more maritime climate and the relative lack of land south of 40°S make the winters milder; thus, snow and ice are less common in inhabited regions of the Southern Hemisphere. In this region, snow occurs every year in elevated regions such as the Andes, the Great Dividing Range in Australia, the mountains of New Zealand, and in the southerlyPatagonia region of South Argentina. Snow occurs year-round inAntarctica.
In theNorthern Hemisphere, some authorities define the period ofwinter based on astronomical fixed points (i.e., based solely on the position of the Earth in its orbit around the Sun), regardless of weather conditions. In one version of this definition, winter begins at thewinter solstice and ends at theMarch equinox.[12] These dates are somewhat later than those used to define the beginning and end of themeteorological winter — usually considered to span the entirety of December, January, and February in the Northern Hemisphere and June, July, and August in the Southern.[12][13]
Astronomically, the winter solstice — being the day of the year that has fewest hours of daylight — ought to be in the middle of the season,[14][15] butseasonal lag means that the coldest period normally follows the solstice by a few weeks. In some cultures, the season is regarded as beginning at the solstice and ending on the followingequinox.[16][17] In the Northern Hemisphere, depending on the year, this corresponds to the period between 20, 21 or 22 December and 19, 20 or 21 March.[12]
In an old Norwegian tradition, winter begins on 14 October and ends on the last day of February.[18]
This system of seasons is based on the length of days exclusively. The three-month period of the shortest days and weakest solar radiation occurs during November, December and January in the Northern Hemisphere and May, June and July in theSouthern Hemisphere.
Many mainland European countries tended to recognizeMartinmas orSt. Martin's Day (11 November) as the first calendar day of winter.[25] The day falls at the midpoint between the old Julian equinox andsolstice dates. Also,Valentine's Day (14 February) is recognized by some countries as heralding the first rites of spring, such as flowers blooming.[26]
The three-month period associated with the coldest average temperatures typically begins somewhere in late November or early December in the Northern Hemisphere and lasts through late February or early March. This "thermological winter" is earlier than the solstice delimited definition, but later than the daylight (Celtic or Chinese) definition. Depending onseasonal lag, this period will vary between climatic regions.
Since by almost all definitions valid for the Northern Hemisphere, winter spans 31 December and 1 January, the season is split across years, just like summer in the Southern Hemisphere. Each calendar year includes parts of two winters. This causes ambiguity in associating a winter with a particular year, e.g. "Winter 2018". Solutions for this problem include naming both years, e.g. "Winter 18/19", or settling on the year the season starts in or on the year most of its days belong to, which is the later year for most definitions.
Ecological reckoning and activity
Thesnowshoe hare, and some other animals, change color in winter.
Ecological reckoning of winter differs from calendar-based by avoiding the use of fixed dates. It is one of six seasons recognized by most ecologists who customarily use the termhibernal for this period of the year (the other ecological seasons being prevernal, vernal, estival, serotinal, and autumnal).[27] The hibernal season coincides with the main period of biological dormancy each year whose dates vary according to local and regional climates in temperate zones of the Earth. The appearance of flowering plants like the crocus can mark the change from ecological winter to the prevernal season as early as late January in mild temperate climates.
To survive the harshness of winter, many animals have developed different behavioral and morphological adaptations foroverwintering:
Hibernation is a state of reducedmetabolic activity during the winter. Some animals "sleep" during winter and only come out when the warm weather returns; e.g.,gophers, frogs, snakes, and bats.
Some animals store food for the winter and live on it instead of hibernating completely. This is the case forsquirrels,beavers,skunks,badgers, andraccoons.
Resistance is observed when an animal endures winter but changes in ways such as color and musculature. The color of the fur or plumage changes to white (in order to be confused with snow) and thus retains itscryptic coloration year-round. Examples are therock ptarmigan,Arctic fox,weasel,white-tailed jackrabbit, andmountain hare.
Some fur-coated mammals grow a heavier coat during the winter; this improves the heat-retention qualities of the fur. The coat is then shed following the winter season to allow better cooling. The heavier coat in winter made it a favorite season fortrappers, who sought more profitable skins.
Snow also affects the ways animals behave; many take advantage of the insulating properties of snow by burrowing in it. Mice andvoles typically live under the snow layer.
Someannual plants never survive the winter. Other annual plants require winter cold to complete their life cycle; this is known asvernalization. As forperennials, many small ones profit from the insulating effects of snow by being buried in it. Larger plants, particularlydeciduous trees, usually let their upper part go dormant, but their roots are still protected by the snow layer. Few plants bloom in the winter, one exception being theflowering plum, which flowers in time forChinese New Year. The process by which plants become acclimated to cold weather is calledhardening.
1683–1684, "The Great Frost", when theThames, hosting theRiver Thames frost fairs, was frozen all the way up toLondon Bridge and remained frozen for about two months. Ice was about 27 cm (11 in) thick in London and about 120 cm (47 in) thick in Somerset. The sea froze up to 2 miles (3.2 km) out around the coast of the southernNorth Sea, causing severe problems for shipping and preventing use of many harbors.
1739–1740, one of the most severe winters in the UK on record. The Thames remained frozen over for about 8 weeks. TheIrish famine of 1740–1741 claimed the lives of at least 300,000 people.[28]
1816 was theYear Without a Summer in the Northern Hemisphere. The unusual coolness of the winter of 1815–1816 and of the following summer was primarily due to the eruption ofMount Tambora in Indonesia, in April 1815. There were secondary effects from an unknown eruption or eruptions around 1810, and several smaller eruptions around the world between 1812 and 1814. The cumulative effects were worldwide but were especially strong in the Eastern United States, Atlantic Canada, and Northern Europe. Frost formed in May in New England, killing many newly planted crops, and the summer never recovered. Snow fell in New York and Maine in June, and ice formed in lakes and rivers in July and August. In the UK, snow drifts remained on hills until late July, and the Thames froze in September. Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in food shortages and the worst famine of the 19th century.
1887–1888: There were record cold temperatures in the Upper Midwest, heavy snowfalls worldwide, and amazing storms, including theSchoolhouse Blizzard of 1888 (in the Midwest in January) and theGreat Blizzard of 1888 (in the Eastern US and Canada in March).
In Europe, the winters of early 1947,[29] February 1956, 1962–1963, 1981–1982, and2009–2010 were abnormally cold. The UK winter of 1946–1947 started out relatively normal but became one of the snowiest UK winters to date, with nearly continuous snowfall from late January until March.
In South America, the winter of 1975 was one of the strongest, with record snow occurring at 25°S in cities of low altitude, with the registration of −17 °C (1.4 °F) in some parts of southern Brazil.
In the eastern United States and Canada, the winter of2013–2014 and the second half of February 2015 were abnormally cold.
1310–1330: Many severe winters and cold, wet summers in Europe, the first clear manifestation of the unpredictable weather of theLittle Ice Age that lasted for several centuries (from about 1300 to 1900). The persistently cold, wet weather caused great hardship, was primarily responsible for theGreat Famine of 1315–1317, and strongly contributed to the weakened immunity and malnutrition leading up to theBlack Death (1348–1350).
1690s: Extremely cold, snowy, severe winters. Ice surroundedIceland for miles in every direction.
1779–1780: Scotland's coldest winter on record, and ice surrounded Iceland in every direction (like in the 1690s). In the United States, a record five-week cold spell bottomed out at −20 °F (−29 °C) inHartford, Connecticut and −16 °F (−27 °C) in New York City. TheHudson River and New York's harbor froze over.
1783–1786: The Thames partially froze, and snow remained on the ground for months. In February 1784, theNorth Carolina was frozen inChesapeake Bay.
1794–1795: A severe winter, with the coldest January in the UK and lowest temperature ever recorded in London: −21 °C (−6 °F) on 25 January. The cold began onChristmas Eve and lasted until late March, with a few temporary warm-ups. The Severn and Thames froze, and frost fairs started up again. The French army tried to invade the Netherlands over its frozen rivers, while the Dutch fleet was stuck in its harbor. The winter had easterlies (fromSiberia) as its dominant feature.
1813–1814: Severe cold, last freeze-over of Thames, and last frost fair. (Removal of old London Bridge and changes to river's banks made freeze-overs less likely.)
1883–1888: Colder temperatures worldwide, including an unbroken string of abnormally cold and brutal winters in the Upper Midwest, related to the explosion ofKrakatoa in August 1883. There was snow recorded in the UK as early as October and as late as July during this period.
1976–1977: One of the coldest winters in the US in decades.
1985: Arctic outbreak in the US resulting from shift inpolar vortex, with many cold temperature records broken.
2002–2003 was an unusually cold winter in the Northern and Eastern US.
2010–2011: Persistent bitter cold in the entire eastern half of the US from December onward, with few or no midwinter warm-ups, and with cool conditions continuing into spring.La Niña and negativeArctic oscillation were strong factors. Heavy and persistent precipitation contributed to almost constant snow cover in the Northeastern US, which finally receded in early May.
2011 was one of the coldest on record inNew Zealand, with sea level snow falling inWellington in July for the first time in 35 years and a much heavier snowstorm for 3 days in a row in August.
Effect on humans
People enjoying the winter weather outdoors inHelsinki,Finland
Humans are sensitive to winter cold, which compromises the body's ability to maintain both core and surface heat of the body.[30] Slipping on icy surfaces is a common cause of winter injuries.[31] Other injuries from the cold include:[32]
Hypothermia — Shivering, leading to uncoordinated movements and death.
Frostbite — Freezing of skin, leading to loss of feeling and damaged tissue.
Trench foot — Numbness, leading to damaged tissue and gangrene.
Chilblains — Capillary damage in digits can lead to more severe cold injuries.
InPersian culture, the winter solstice is calledYaldā (meaning: birth) and has been celebrated for thousands of years. It is referred to as the eve of the birth ofMithra, who symbolised light, goodness and strength on Earth.
InGreek mythology,Hades kidnappedPersephone to be his wife.Zeus ordered Hades to return her toDemeter, the goddess of the Earth and her mother. Hades tricked Persephone into eating the food of the dead, so Zeus decreed that she spend six months with Demeter and six months with Hades. During the time her daughter is with Hades, Demeter became depressed and caused winter.
^"winter".Encyclopædia Britannica. 16 September 2022. Retrieved28 October 2022.
^"solstice".Encyclopædia Britannica. Retrieved28 October 2022.
^"Første vinterdag".The Norwegian Meteorological Institute (in Norwegian). 14 October 2008. Archived fromthe original on 29 June 2011. Retrieved31 August 2009.
^"Seasons".Meteorological Glossary. Australian Bureau of Meteorology.Archived from the original on 7 March 2009. Retrieved21 June 2009.
^Anderson, Earl R. (2003).Folk-Taxonomies in Early English. Madison, N.J.: Fairleigh Dickinson University Press. p. 219.ISBN978-0-8386-3916-0.On St. Martin's day (11 November) winter begins, summer takes its end, harvest is completed. ...This text is one of many that preserves vestiges of the ancient Indo-European system of two seasons, winter and summer.
.jpg)
.jpg)
