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A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24 hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year.
A cold wave can cause death and injury to livestock and wildlife. Exposure to cold mandates greater caloric intake for all animals, including humans, and if a cold wave is accompanied by heavy and persistent snow, grazing animals may be unable to reach needed food and die of hypothermia or starvation. They often necessitate the purchase of foodstuffs at considerable cost to farmers to feed livestock.
The belief that more deaths are caused by cold weather in comparison to hot weather is true as a result of the after effects of these temperatures (i.e. cold, flu, pneumonia, etc.) all contributing factors to hypothermia. However statistics have shown that more deaths occur during a heat wave than in a cold snap in developed regions of the world. Studies have shown that these numbers are significantly higher in undeveloped regions.
Extreme winter cold often causes poorly insulated water pipelines and mains to freeze. Even some poorly protected indoor plumbing ruptures as water expands within them, causing much damage to property and costly insurance claims. Demand for electrical power and fuels rises dramatically during such times, even though the generation of electrical power may fail due to the freezing of water necessary for the generation of hydroelectricity. Some metals may become brittle at low temperatures. Motor vehicles may fail as antifreeze fails and motor oil gels, resulting even in the failure of the transportation system. To be sure, such is more likely in places like Siberia and much of Canada that customarily get very cold weather.
Fires become even more of a hazard during extreme cold. Water mains may break and water supplies may become unreliable, making firefighting more difficult. The air during a cold wave is typically denser and any cold air that a fire draws in is likely to cause a more intense fire because the colder, denser air contains more oxygen.
Winter cold waves that aren't considered cold in some areas, but cause temperatures significantly below average for an area, are also destructive. Areas with subtropical climates may recognize unusual cold, perhaps barely freezing, temperatures, as a cold wave. In such places, plant and animal life is less tolerant of such cold as may appear rarely. The same winter temperatures that one associates with the norm for Kentucky, northern Utah, or Bavaria would be catastrophic to winter crops in southern Florida, southern Arizona, or southern Spain that might be grown for wintertime consumption farther north, or to such all-year tropical or subtropical crops as citrus fruits. Likewise, abnormal cold waves that penetrate into tropical countries in which people do not customarily insulate houses or have reliable heating may cause hypothermia and even frostbite.
Cold waves that bring unexpected freezes and frosts during the growing season in mid-latitude zones can kill plants during the early and most vulnerable stages of growth, resulting in crop failure as plants are killed before they can be harvested economically. Such cold waves have caused famines. At times as deadly to plants as drought, cold waves can leave a land in danger of later brush and forest fires that consume dead biomass. One extreme was the so-called Year Without a Summer of 1816, one of several years during the 1810s in which numerous crops failed during freakish summer cold snaps after volcanic eruptions that reduced incoming sunlight.
In some places, such as Siberia, extreme cold requires that fuel-powered machinery to be used even part-time must be run continuously. Internal plumbing can be wrapped, and persons can often run water continuously through pipes. Energy conservation, difficult as it is in a cold wave, may require such measures as collecting people (especially the poor and elderly) in communal shelters. Even the homeless may be arrested and taken to shelters, only to be released when the hazard abates. Hospitals can prepare for the admission of victims of frostbite and hypothermia; schools and other public buildings can be converted into shelters.
People can stock up on food, water, and other necessities before a cold wave. Some may even choose to migrate to places of milder climates, at least during the winter. Suitable stocks of forage can be secured before cold waves for livestock, and livestock in vulnerable areas might be shipped from affected areas or even slaughtered. Smudge pots can bring smoke that prevents hard freezes on a farm or grove. Vulnerable crops may be sprayed with water that will paradoxically protect the plants by freezing and absorbing the cold from surrounding air.
Most people can dress appropriately and can even layer their clothing should they need to go outside or should their heating fail. They can also stock candles, matches, flashlights, and portable fuel for cooking and wood for fireplaces or wood stoves, as necessary. However caution should be taken as the use of charcoal fires for cooking or heating within an enclosed dwelling is extremely dangerous due to carbon monoxide poisoning. Adults must remain aware of the exposure that children and the elderly have to cold.
Historical cold waves
Contemporary cold waves (2001-date)
- Early 2012 European cold wave - As of February 11, 2012 at least 590 people died during a cold snap with temperatures falling below −35 °C (−31 °F) in some regions. Ukraine is the worst hit, with over 100 deaths related to the cold.
- Winter of 2010–2011 in Great Britain and Ireland - It was referred to as The Big Freeze by national medias in both United Kingdom and Ireland and it was the coldest winter in Britain for 31 years with an average temperature of 1.51 °C (34.72 °F). The UK had its coldest December ever, since records began in 1910, with a mean temperature of −1 °C (30.2 °F). It easily broke the previous record of 0.1 °C (32.18 °F), set in December 1981.
- A cold wave affected much of the Deep South in the United States and well into Florida in January and February 2010.
- 2009-2010 European Cold Wave - At least 90 are confirmed dead after record low temperatures and heavy snowfall across Europe causes travel disruption to much of the continent including the British Isles, France, the Low Countries, Germany, Austria, Italy, Poland, the Baltic States, the Balkans, Ukraine and Russia. Coldest winter for 30 years in the UK with the longest sustained cold spell since 1981. Temperatures in the Italian Alpine peaks have reached low to an extreme of −47 °C (−52.6 °F).
- Early 2009 European Cold Wave - Early January gave most of Europe, especially in central and south very cold temperatures. Some places like Germany, France, Italy, Romania and Spain had record cold temperatures well below 0 °C (32 °F). Most of the places were covered in snow and ice which caused school closings and airport delays. Large cities like Paris, Madrid, Berlin and even Marseille saw very cold temperatures with lots of snow and ice in Northern Italy, most of Germany, in northern Portugal and even along the coasts of the Mediterranean. In early February another cold front brought heavy snowfall to much of Western Europe with the heaviest snow falling in France, Northern Italy, the Low Countries and the United Kingdom, where parts of Southern England had seen the worst snowfall in over 18 years causing widespread travel disruption particularly around London.
- 2008 Alaska Cold Wave- In early February, Alaska experienced some of the coldest temperatures for 8 years, with Fairbanks nearing −50 °F (−45.6 °C) and Chicken, Alaska bottoming out at −72 °F (−57.8 °C), a mere eight degrees Fahrenheit change (4.4 °C) away from the record of −80 °F (−62.2 °C). The first half of January also brought unusual cold weather and heavy snow to widespread regions of China and the Middle East.
- 2007 Argentine cold wave - An interaction with an area of low pressure systems across Argentina during the July 6, July 7 and 8 of 2007, and the entry of a massive polar cold snap resulted in severe snowfalls and blizzards, and recorded temperatures below −32 °C (−26 °F). The cold snap advanced from the south towards the central zone of the country, continuing its displacement towards the north during Saturday, July 7. On Monday July 9, the simultaneous presence of very cold air, gave place to the occurrence of snowfalls. This phenomenon left at least 23 people dead.
- 2007 Northern Hemisphere cold wave - All of Canada and most of the United States underwent a freeze after a two-week warming that took place in late March & early April. Crops froze, wind picked up, and snow drizzled much of the United States. Some parts of Europe also experienced unusual cold winter-like temperatures, during that time.
- 2005-2006 European cold wave - Eastern Europe and Russia saw a very cold winter. Some of them saw their coldest on record or since the 1970s. Snow was an abundance in unusual places, such as in southern Spain and Northern Africa. All the winter months that season saw temperatures well below average across the continent.
- 2004-2005 Southern Europe cold wave - All areas of Southern Europe saw an unusually hard winter. This area saw an ice storm which have a 1 in 1000 chance of happening. This cold front caused snow in Algeria, which is extremely unusual. The south of Spain and Morocco also recorded freezing temperatures, and record freezing temperatures were observed on the north of Portugal and Spain.
- 2004 January cold outbreak, Northeast United States - New England was near a record month when frequent Arctic fronts caused unusually cold weather. Boston was one of their coldest in 114 years. Virginia Beach had an unusually long period of below freezing weather. One area of New York saw 150 inches (381 cm) of snow in a month. Many parts of the western and midwestern area of the country seen the effect as well.
20th-century cold waves
- 1997 Northern Plains cold air Outbreak - Mid January across the Northern U.S. was one of the windiest on record. With a low of around −40 °F (−40.0 °C) in some places, wind caused bitterly cold wind chills sometimes nearing −80 °F (−62.2 °C). Northern parts of North Dakota saw up to 90 inches (230 cm) of snow. This was one of the most severe cold-air outbreaks of the 1990s.
- 1996 Great Midwest cold outbreak - Late January and early February was Northern Minnesota's coldest short term period on record. The record low of −60 °F (−51.1 °C) was recorded in Tower, Minnesota. Cities like Minneapolis experience temperatures near −35 °F (−37.2 °C).
- 1995 White Earthquake in southern Chile - On August 1995 southern Chile was struck by a cold wave consisting in two successive cold fronts. Fodder scarcity caused a severe livestock starvation. Cows and sheep were also buried in snow. In parts of Tierra del Fuego up to 80% of the sheep livestock died.
- 1994 Northern US/Southern Canada cold outbreak - January 1994 was the coldest month recorded over many parts of the northeast and north-central United States, as well as Southern Canada, or coldest since the late 1970s in some locations. Many overnight record lows were set. Cold outbreaks continued into February but the severity eased somewhat. The cold also extended further south than usual into Texas bringing snowfall and temperatures lower than −20 °F (−28.9 °C) to parts of the state, Florida also experienced cold and snowfall, even once flurries were reported north of Miami and damage to the citrus crop in central Florida was extensive. Detroit, Michigan saw their coldest temperature since 1985.
- 1990 western United States- Extreme cold dropped down from Canada in the second half of December, causing record low temperatures up and down the West Coast, including one of California's most damaging freezes on record.
- 1989 record cold start to December - In 1989, the central and eastern USA saw one of the coldest Decembers on record. A White Christmas occurred.
- 1985 Great Western cold air outbreak - February 1985 saw the USA's third coldest temperature of −69 °F (−56.1 °C) in Peter's Sink, Utah. About a month of severe cold affect a large part of the nation. 1985 became the fourth coldest year on record in the western USA.
- January 1985 US cold air outbreak - On January 21, 1985, it was so cold that President Ronald Reagan's inauguration took place in the Capitol Rotunda. In addition to the cold in Washington, DC, frost was reported in Miami and many Southern cities set all-time record cold or at least came close.
- 1983 Record cold December USA - USA had its coldest ever Christmas in 1983. Severely cold winds blew in from Canada and about 70% of the month was colder than average. The 1980s saw the USA's coldest Decembers on record. Many locations east of the Rockies broke December cold records on Christmas Eve. In addition to −23 °F (−30.6 °C) cold, the Sioux Falls area had 60 mph (97 km/h) winds bringing wind chills down to −70 °F (−56.7 °C). High temperatures did not even reach −10 °F (−23.3 °C) in northern Illinois during the days before Christmas. Temperatures dropped below 0 °F (−17.8 °C) on December 15 and remained there for over 9 days at Sioux Falls. Minneapolis recorded an average temperature for the month of 3.7 °F (−15.7 °C), the coldest on record.
- 1982 cold air outbreak - January 1982 was very cold. The 1981 AFC Championship Game, held in Cincinnati was nicknamed the "Freezer Bowl" due to the −9 °F (−22.8 °C) temperature and −59 °F (−50.6 °C) wind chill. The following week's events was also known as Cold Sunday
- 1970s - In the late 1970s most or all places in the Lower 48 had at least one winter with a memorable cold wave, and the winter of 1978-79 was the coldest on record in the lower 48, with every state seeing well below average temperatures.
- 1936 Cold wave - The cold wave of 1936 was the only cold wave of the 1930s impacting North America and the Midwest United States.
- 1910s - The severe 1912 United States cold wave caused the longest recorded period of below-zero weather. The winter from 1916–1917 until 1917–1918 was very frigid across the USA.
- "Cold Wave". AMS - Glossary of Meteorology. Retrieved 2008-09-25.
- "Police law of Finland 11§" (in Finnish). Retrieved 2008-09-25.
- name="Pidd, Helen & Elder, Helen" The Guardian: European Cold Snap Threatens Energy Crisis as Death Toll Rises"
- name="" Kyiv Post: Ukraine Cold Spell Death Toll Rises 101
- Cormier, Bill Buenos Aires Gets First Snow Since 1918, Associated Press via Breitbart.com, July 7, 2007
- Cold snap in Argentina leads to energy crunch that idles factories, triggers blackouts, AP via International Herald Tribune, May 31, 2007
- Record cold December
- Minneapolis December weather records
|Wikivoyage has a travel guide for Travelling in cold weather.|