Editing Winter (section)

==Meteorological reckoning==
{{further|Meteorological seasons}}
[[File:Earth-satellite-seasons.gif|thumb|upright=1.3|Animation of snow cover changing with the seasons]]

'''Meteorological reckoning''' is the method of measuring the winter season used by [[meteorologists]] based on "sensible weather patterns" for record keeping purposes,<ref>{{cite web |last=Huttner |first=Paul |url=http://minnesota.publicradio.org/collections/special/columns/updraft/archive/2007/12/instant_meteorological_winter.shtml |title=Instant meteorological winter |publisher=Minnesota Public Radio |date=6 December 2007 |access-date=22 December 2011 |url-status=live |archive-url=https://web.archive.org/web/20110608125101/http://minnesota.publicradio.org/collections/special/columns/updraft/archive/2007/12/instant_meteorological_winter.shtml |archive-date=8 June 2011 |df=dmy-all }}</ref> so the start of meteorological winter varies with latitude.<ref>{{cite web |url=http://www.noaanews.noaa.gov/stories2003/s2143.htm |title=Winter's Been Here Despite What the Calendar Says |publisher=NOAA Magazine |date=22 December 2003 |access-date=22 December 2011 |url-status=live |archive-url=https://web.archive.org/web/20110716220559/http://www.noaanews.noaa.gov/stories2003/s2143.htm |archive-date=16 July 2011 |df=dmy-all }}</ref> 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 the [[Northern Hemisphere]], and June, July and August in the [[Southern 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 of [[Precipitation (meteorology)|precipitation]] as well as prolonged dampness because of permanent snow cover or high precipitation rates coupled with low temperatures, precluding evaporation. [[Blizzard]]s often develop and cause many transportation delays. [[Diamond dust]], also known as ice needles or ice crystals, forms at temperatures approaching {{convert|-40|C|F}} due to air with slightly higher moisture from above mixing with colder, surface-based air.<ref name="glossdia">{{cite web|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=diamond+dust&submit=Search|author=Glossary of Meteorology|date=June 2000|title=Diamond Dust|publisher=[[American Meteorological Society]]|access-date=21 January 2010|url-status=dead|archive-url=https://web.archive.org/web/20090403084329/http://amsglossary.allenpress.com/glossary/search?p=1&query=diamond+dust&submit=Search|archive-date=3 April 2009|df=dmy-all}}</ref> They are made of simple hexagonal ice crystals.<ref>{{cite journal|url=http://eands.caltech.edu/articles/Libbrecht%20Feature.pdf|page=12|year=2001|author=Kenneth G. Libbrecht|title=Morphogenesis on Ice: The Physics of Snow Crystals|journal=Engineering & Science|access-date=21 January 2010|issue=1|url-status=dead|archive-url=https://web.archive.org/web/20100625192032/http://eands.caltech.edu/articles/Libbrecht%20Feature.pdf|archive-date=25 June 2010|df=dmy-all}}</ref> 

The [[SMHI|Swedish Meteorological Institute]] (SMHI) defines ''thermal winter'' as when the daily mean temperatures are below {{convert|0|C|F}} for five consecutive days.<ref>{{cite web|url=http://www.smhi.se/kunskapsbanken/vinter-1.1480|title=Vinter|publisher=SMHI|language=sv|access-date=31 July 2015|url-status=dead|archive-url=https://web.archive.org/web/20150325164811/http://www.smhi.se/kunskapsbanken/vinter-1.1480|archive-date=25 March 2015|df=dmy-all}}</ref> 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.<ref>{{cite web|url=http://data.smhi.se/met/climate/time_series/month/vov_pdf/SMHI_vov_precipitation_sunshine_jan15.pdf?71642|title=Nederbörd, Solsken och Strålning – Januari 2015|trans-title=Precipitation, Sunshine & Radiation - January 2015 (all-time records section)|language=sv|publisher=SMHI|access-date=31 July 2015|archive-url=https://web.archive.org/web/20191026123924/http://data.smhi.se/met/climate/time_series/month/vov_pdf/SMHI_vov_precipitation_sunshine_jan15.pdf?71642|archive-date=26 October 2019|url-status=dead}}</ref><ref>{{cite web|url=http://data.smhi.se/met/climate/time_series/month/vov_pdf/SMHI_vov_temperature_wind_jan15.pdf?18701|title=Januari 2015 – Lufttemperatur och Vind|trans-title=January 2015 – Temperature & Wind (all-time records section)|language=sv|publisher=SMHI|access-date=31 July 2015|archive-url=https://web.archive.org/web/20191026123844/http://data.smhi.se/met/climate/time_series/month/vov_pdf/SMHI_vov_temperature_wind_jan15.pdf?18701|archive-date=26 October 2019|url-status=dead}}</ref>

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 southerly [[Patagonia]] region of South Argentina. Snow occurs year-round in [[Antarctica]].