Ontario

=== Climate ===
{{See also|Climate of Ontario}}
[[File:Ontario Köppen.svg|left|thumb|upright=1.3|[[Köppen climate classification|Köppen climate types]] of Ontario]]
Ontario's climate varies by season and location.<ref name=EC>{{cite web |url=http://www.on.ec.gc.ca/canada-country-study/intro.html |archive-url=https://web.archive.org/web/20130323131703/http://www.on.ec.gc.ca/canada-country-study/intro.html |archive-date = March 23, 2013 |title = The Canada Country Study: Climate Impacts and Adaptation: Ontario Region Executive Summary |publisher = Environment Canada |access-date = January 29, 2013}}</ref> Three air sources affect it: cold, dry, arctic air from the north (dominant factor during the winter months, and for a longer part of the year in far northern Ontario); Pacific polar air crossing in from the western Canadian Prairies/US [[Northern Plains]]; and warm, moist air from the Gulf of Mexico and the Atlantic Ocean.<ref name=UBCgeo>{{cite web |first1 = David |last1 = Baldwin |first2 = Joseph |last2 = Desloges |first3 = Lawrence |last3 = Band |url=http://www.ubcpress.ca/books/pdf/chapters/ecology/chapter2.pdf |title = Physical Geography of Ontario |publisher = UBC Press |access-date = March 25, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20071217184751/http://www.ubcpress.ca/books/pdf/chapters/ecology/chapter2.pdf |archive-date = December 17, 2007 |df = mdy-all }}</ref> The effects of these major air masses on temperature and precipitation depend mainly on latitude, proximity to major bodies of water and to a small extent, terrain relief.<ref name= UBCgeo/> In general, most of Ontario's climate is classified as humid continental.<ref name= UBCgeo/>

Ontario has three main climatic regions:
* The surrounding Great Lakes greatly influence the climatic region of southern Ontario.<ref name="EC"/> During the fall and winter, the release of heat stored by the lakes moderates the climate near the shores.<ref name=EPA>{{cite web |url=http://www.epa.gov/glnpo/atlas/glat-ch2.html |title = Natural Processes in the Great Lakes |publisher = US Environmental Protection Agency |access-date = March 25, 2013 |url-status=live |archive-url=https://web.archive.org/web/20130202002550/http://www.epa.gov/glnpo/atlas/glat-ch2.html |archive-date = February 2, 2013 |df = mdy-all }}</ref> This gives parts of southern Ontario milder winters than mid-continental areas at lower latitudes.<ref name= EPA/> Parts of Southwestern Ontario and the Niagara region (generally south of a line from Sarnia–Toronto) have a moderate [[humid continental climate]] ([[Köppen climate classification]] ''Dfa''), similar to the inland [[Mid-Atlantic states]] and the [[Great Lakes]] portion of the [[Midwestern United States]]. The region has warm to hot, humid summers and cold winters. Annual precipitation ranges from {{convert|750|-|1000|mm|in|abbr=on}} and is well distributed throughout the year. Most of this region lies in the lee of the Great Lakes, making for abundant snow in some areas. In December 2010, the [[snowbelt]] set a new record when it was hit by more than a metre of snow within 48 hours.<ref>{{cite news |url=http://www.cbc.ca/news/canada/snowstorm-shuts-down-london-ont-1.929437 |work=CBC News |title=Snowstorm shuts down London, Ont |date=December 8, 2010 |url-status=live |archive-url=https://web.archive.org/web/20140308071854/http://www.cbc.ca/news/canada/snowstorm-shuts-down-london-ont-1.929437 |archive-date=March 8, 2014 }}</ref>
* The next climatic region is Central and Eastern Ontario, which has a moderate [[humid continental climate]] (Köppen ''Dfb''). This region has warm and sometimes hot summers with colder, longer winters, ample snowfall (even in regions not directly in the snowbelts) and annual precipitation similar to the rest of Southern Ontario.<ref name="UBCgeo" />

In the northeastern parts of Ontario, extending south as far as [[Kirkland Lake]], the cold waters of Hudson Bay depress summer temperatures, making it cooler than other locations at similar latitudes. The same is true on the northern shore of [[Lake Superior]], which cools hot, humid air from the south, leading to cooler summer temperatures.<ref name= UBCgeo/> Along the eastern shores of Lake Superior and [[Lake Huron]] winter temperatures are slightly moderated but come with frequent heavy [[lake-effect snow]] squalls that increase seasonal snowfall totals to upwards of {{convert|3|m|ft|0|abbr=on}} in some places. These regions have higher annual precipitation, in some places over {{convert|100|cm|in|abbr=on}}.
[[File:Lake Effect Snow on Earth.jpg|thumb|Cold northwesterly wind over the [[Great Lakes]] creating [[lake-effect snow]]. Lake-effect snow most frequently occurs in the [[snowbelt]] regions of the province.]]
* The northernmost parts of Ontario&nbsp;– primarily north of 50°N&nbsp;– have a [[subarctic climate]] (Köppen ''Dfc'') with long, severely cold winters and short, cool to warm summers with dramatic temperature changes possible in all seasons. With no major mountain ranges blocking sinking Arctic [[air mass]]es, temperatures of {{convert|-40|C|abbr=on}} are not uncommon; snow remains on the ground for sometimes over half the year. Snow accumulation can be high in some areas.<ref name= EC/> Precipitation is generally less than {{convert|70|cm|in|abbr=on}} and peaks in the summer months in the form of rain or thunderstorms.<ref name= EC/>

Severe thunderstorms peak in summer. [[Windsor, Ontario|Windsor]], in [[Southern Ontario|Southern]] [[Southwestern Ontario|(Southwestern)]] Ontario, has the most lightning strikes per year in Canada, averaging 33 days of thunderstorm activity per year.<ref>{{cite web|title=WeatherStats: Weather Winners|url=https://www.weatherstats.ca/winners.html?location=ottawa;category=35|access-date=June 29, 2020|website=Amateur Weather Statistics for Ottawa (Kanata – Orléans), Ontario|archive-date=June 30, 2020|archive-url=https://web.archive.org/web/20200630180809/https://www.weatherstats.ca/winners.html?location=ottawa;category=35|url-status=live}}</ref> In a typical year, Ontario averages 11 confirmed [[tornado]] touchdowns. Ontario had a record 29 tornadoes in both 2006 and 2009. [[Tropical cyclone|Tropical depression]] remnants occasionally bring heavy rains and winds in the south, but are rarely deadly. A notable exception was [[Hurricane Hazel]] which struck Southern Ontario centred on Toronto, in October 1954.{{Citation needed|date=April 2024}}

{|class="wikitable sortable"
|+Average daily maximum and minimum temperatures for selected locations in Ontario
|-
!City
!July (°C)
!July (°F)
!January (°C)
!January (°F)
|-
|[[Windsor, Ontario|Windsor]] ([[Windsor International Airport]])<ref name="ccnwindsor">{{cite web |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4716&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |title = Windsor A, Ontario |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011 |publisher = Environment Canada |access-date = April 12, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140413133907/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4716&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |archive-date = April 13, 2014 |df = mdy-all }}</ref> ||28/18 ||82/64 ||0/−7 ||31/19
|-
|[[Niagara Falls, Ontario|Niagara Falls]] (NPCSH)<ref name="ccnniagara">{{cite web |publisher = [[Environment Canada]] |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4659&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |title = Niagara Falls NPCSH |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011|access-date = April 12, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140413160109/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4659&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |archive-date = April 13, 2014 |df = mdy-all }}</ref> ||27/17 ||81/63 ||0/−8 ||30/18
|-
|[[Toronto]] ([[The Annex]])<ref name="ccnannex">{{cite web |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=5051&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |title= 1981 to 2010 Canadian Climate Normals |publisher= Environment Canada |id= Climate ID: 6158350 |date= February 13, 2014 |access-date= February 24, 2014 |url-status=live |archive-url=https://web.archive.org/web/20160403002422/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=5051&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |archive-date= April 3, 2016 |df= mdy-all }}</ref> ||27/18 ||80/64 ||−1/−7 ||30/20
|-
|[[Midland, Ontario|Midland]] (Water Pollution Control Plant)<ref name="ccnmidland">{{cite web |publisher = [[Environment Canada]] |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4474&lang=e&amp;StationName=Midland&amp;SearchType=Contains&amp;stnNameSubmit=go&dCode=5&dispBack=1 |title = Midland Water Pollution Control Plant |work = Canadian Climate Normals 1981–2010 |date = September 25, 2013|access-date = May 9, 2016 |url-status=live |archive-url=https://web.archive.org/web/20170517214728/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4474&lang=e&StationName=Midland&SearchType=Contains&stnNameSubmit=go&dCode=5&dispBack=1 |archive-date = May 17, 2017 |df = mdy-all }}</ref> ||26/16 ||78/61 ||−4/–13 ||25/8
|-
|[[Ottawa]] ([[Ottawa Macdonald–Cartier International Airport]])<ref name="ccnottawa">{{cite web |publisher = Environment Canada |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4337&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |title = Ottawa Macdonald Cartier Int'l A, Ontario |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011|access-date = May 8, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140509001426/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4337&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |archive-date = May 9, 2014 |df = mdy-all }}</ref> ||27/16 ||80/60 ||−6/−14 ||22/6
|-
|[[Greater Sudbury|Sudbury]] ([[Sudbury Airport]])<ref name="ccnsudbury">{{cite web |publisher = [[Environment Canada]] |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4132&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |title = Sudbury A, Ontario |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011|access-date = April 12, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140413160052/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4132&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12 |archive-date = April 13, 2014 |df = mdy-all }}</ref> ||25/13 ||77/56 ||−8/−19 ||18/0
|-
|[[Emo, Ontario|Emo]] (Emo Radbourne)<ref name="ccnemo">{{cite web |publisher = [[Environment Canada]] |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=3928&lang=e&StationName=Emo&SearchType=Contains&stnNameSubmit=go&dCode=0 |title = Emo Radbourne |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011|access-date = May 9, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160604225741/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=3928&lang=e&StationName=Emo&SearchType=Contains&stnNameSubmit=go&dCode=0 |archive-date = June 4, 2016 |df = mdy-all }}</ref> ||25/11 ||77/52 ||−9/–22 ||15/–9
|-
|[[Thunder Bay]] ([[Thunder Bay International Airport]])<ref name="ccnthunder">{{cite web |publisher = [[Environment Canada]] |url = http://ftp/ |title = Thunder Bay A |work = Canadian Climate Normals 1981–2010 |format = CSV |access-date = September 29, 2013 |archive-date = October 10, 2007 |archive-url = https://web.archive.org/web/20071010064342/http://ftp%23fifa.ns1.ensim.hu/ |url-status = live }}</ref> ||24/11 ||76/52 ||−9/−21 ||18/−5
|-
|[[Kenora]] ([[Kenora Airport]])<ref name="ccnkenora">{{cite web|publisher = [[Environment Canada]]|url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=3960&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12|title = Kenora Airport|work = Canadian Climate Normal's 1981–2010|access-date = April 9, 2014|date = 2011|url-status=live|archive-url=https://web.archive.org/web/20140413160135/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=3960&lang=e&dCode=1&province=ONT&provBut=Go&month1=0&month2=12|archive-date = April 13, 2014|df = mdy-all}}</ref> ||24/15 ||76/59 ||−11/−21 ||12/−5
|-
|[[Moosonee]] (UA)<ref name="ccnmoosonee">{{cite web |publisher = [[Environment Canada]] |url=http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4168&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |title = Moosonee UA |work = Canadian Climate Normals 1981–2010 |date = October 31, 2011|access-date = April 9, 2014 |url-status=live |archive-url=https://web.archive.org/web/20140413160113/http://climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?stnID=4168&lang=e&dCode=0&province=ONT&provBut=Go&month1=0&month2=12 |archive-date = April 13, 2014 |df = mdy-all }}</ref> ||23/9 ||73/48 ||−14/–26 ||8/–15
|}