Editing Weather forecasting (section)

===Utility companies===
[[File:Air handling unit.JPG|thumb|right|An [[air handling unit]] is used for the heating and cooling of air in a central location (click on image for legend).]]
{{Main|Degree day}}
Electricity and gas companies rely on weather forecasts to anticipate demand, which can be strongly affected by the weather. They use the quantity termed the degree day to determine how strong of a use there will be for heating ([[heating degree day]]) or cooling (cooling degree day). These quantities are based on a daily average temperature of {{convert|65|F}}. Cooler temperatures force heating degree days (one per degree Fahrenheit), while warmer temperatures force cooling degree days.<ref>[[Climate Prediction Center]]. [http://www.cpc.noaa.gov/products/analysis_monitoring/cdus/degree_days/ddayexp.shtml "Degree Day Explanation"] {{Webarchive|url=https://web.archive.org/web/20100524040629/http://www.cpc.noaa.gov/products/analysis_monitoring/cdus/degree_days/ddayexp.shtml |date=May 24, 2010 }}. Retrieved May 25, 2008.</ref> In winter, severe cold weather can cause a surge in demand as people turn up their heating.<ref>{{cite news |date=February 26, 1993 |newspaper=[[The New York Times]] |url=https://www.nytimes.com/1993/02/26/business/futures-options-cold-weather-brings-surge-in-prices-of-heating-fuels.html |title=Futures/Options; Cold Weather Brings Surge in Prices of Heating Fuels |access-date=May 25, 2008 |archive-date=June 15, 2018 |archive-url=https://web.archive.org/web/20180615135320/https://www.nytimes.com/1993/02/26/business/futures-options-cold-weather-brings-surge-in-prices-of-heating-fuels.html |url-status=live }}</ref> Similarly, in summer a surge in demand can be linked with the increased use of [[air conditioning]] systems in hot weather.<ref>[[BBC News]] (July 25, 2006) [http://news.bbc.co.uk/2/hi/uk_news/5212724.stm "Heatwave causes electricity surge"] {{Webarchive|url=https://web.archive.org/web/20170629200832/http://news.bbc.co.uk/2/hi/uk_news/5212724.stm |date=June 29, 2017 }}. Retrieved May 25, 2008.</ref> By anticipating a surge in demand, utility companies can purchase additional supplies of power or natural gas before the price increases, or in some circumstances, supplies are restricted through the use of [[Brownout (electricity)|brownouts]] and [[Power outage|blackouts]].<ref>Toronto Catholic Schools. [http://www.tcdsb.org/environment/energydrill/EDSP_KeyMessages_FINAL.pdf "The Seven Key Messages of the Energy Drill Program"]. Retrieved May 25, 2008. {{webarchive|url=https://web.archive.org/web/20120217042744/http://www.tcdsb.org/environment/energydrill/EDSP_KeyMessages_FINAL.pdf |date=February 17, 2012 }}</ref>