The Regina Cyclone, or Regina tornado of 1912, was a tornado that devastated the city of Regina, Saskatchewan, Canada, on Sunday, June 30, 1912. It remains the deadliest tornado in Canadian history with a total of 28 fatalities and about 300 people injured. At about 4:50 p.m., green funnel clouds formed and touched down south of the city, tearing through the residential area between Wascana Lake and Victoria Avenue, and continuing through the downtown business district, rail yards, warehouse district, and northern residential area.

The tornado formed 18 kilometres (11 mi) south of the city and continued for another 12 kilometres (7.5 mi) north of the city before dissipating. It was approximately 150 metres (490 ft) wide. The tornado's wind velocity has been estimated at 400 kilometres per hour (250 mph), making it the equivalent of a high-end F4 on the Fujita Scale. The tornado also displayed a multiple vortex structure throughout the city's residential areas, leaving individual houses untouched next to homes that were completely flattened.

The tornado hit Regina at approximately 5:00 p.m. on June 30, 1912. The tornado formed 18 km south of the city and was roughly 150 metres wide by the time it reached Regina. The worst damage was in the residential area north of Wascana Lake and the central business district. Many buildings, both brick and wood, were entirely destroyed. "The new Central Library building was opened May 11, 1912, and just six weeks later, the new library was among the many buildings that suffered damage."

"In just twenty minutes it completely leveled a number of houses, and caused other houses to explode as the pressure inside the structures rose when the tornado passed overhead." The affluent residential area to the south was substantially diminished, but the tornado left houses untouched here and there immediately adjacent to houses which were flattened. "[I]n the warehouse district, it destroyed many of the storage buildings. The CPR Roundhouse was stripped to the rafters, and boxcars were pulled from the tracks and hurtled into the air."

Such damage was especially appalling to see as well as experience since Regina had been built on an entirely featureless plain, lacking any trees or vegetation other than natural wild prairie grass and without any hills or rivers apart from the tiny spring runoff Wascana Creek, which only flowed in early spring.

"The cyclone claimed twenty-eight lives and was the worst in Canadian history in terms of deaths. It also rendered 2,500 persons temporarily homeless, and caused over $1,200,000 in property damage. It took the city two years to repair the damage and ten years to pay off its storm debt."

The city forced those rendered homeless by the disaster to pay for the nightly use of cots set up in schools and city parks. It also required homeowners to pay for the removal of rubble from their homes. Debris was cleaned up rather quickly. "The storm damaged the Metropolitan Methodist Church, [the Knox Presbyterian Church, the First Methodist,] the library, the YWCA [and YMCA], and numerous other downtown buildings; in the warehouse district, it destroyed many of the storage buildings.

Damage from the tornado is estimated to be F4 on the Fujita scale. The tornado killed 28 people, injured hundreds, and left 2,500 people homeless, out of a population of about 30,213 (in 1911). Around 500 buildings were destroyed or damaged. Property damage was quantified at $1.2 million CAD, and it would be forty years before the $4.5 million CAD private and public debt incurred to rebuild and repair was repaid.

The only remaining "souvenir" of this event is different-coloured bricks on the north wall of Regina's Knox-Metropolitan United Church (the former Metropolitan Methodist church). The bricks show where the wall was rebuilt after its tornado-caused collapse. Knox Presbyterian, Metropolitan Methodist and First Baptist, all being brick, were rebuilt after the tornado. Knox and Metropolitan both became United Church in 1925, and merged their congregations in 1951 to become the Knox-Metropolitan Church, meeting in the old Metropolitan Church. The Knox building was ultimately demolished.

Boris Karloff, Jeanne Russell, Henrietta Crosman, and the Albini-Avolos are all characters in BD Miller's musical drama, "Swept Off Our Feet: Boris Karloff and the Regina Cyclone", which commemorated the 100th anniversary of the disaster and premiered as a July 2012 production of Regina Summer Stage.

The novel Euphoria by Connie Gault won the 2009 Saskatchewan Book Award for Fiction and prominently features the Regina Cyclone.

A chapter of Frank Rasky's book Great Canadian Disasters (1961) is devoted to this tragedy.

• List of Canadian tornadoes and tornado outbreaks

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  Winnipeg Elevator after the tornado
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  Warehouse district after the tornado
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  Side view of Princess Theatre after tornado
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  Regina Tornado June 30, 1912
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  Regina downtown after tornado
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  People in front of damaged building
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  Metropolitan Methodist Church after the tornado
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  Damage to Metropolitan Methodist Church
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  North end of Regina after tornado
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  Downtown stores damaged by tornado
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  Destroyed Winnipeg Elevator Company buildings
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  Damaged office building after tornado
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  Damaged homes on Smith Street
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  Damage to the YWCA immediately north of Metropolitan Methodist Church on Lorne Street
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  Damage to buildings after the tornado
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  Damage to businesses after the tornado
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  Damage to buildings on Lorne St.
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  Damage caused by the tornado
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  Two uniformed men stand on a sidewalk in front of a row of damaged houses.

• Brennan, Patrick H. (2004). "It's an Ill Wind that Blows Nobody Good: Regina's 1912 "Cyclone"". Harms' way : disasters in Western Canada. Calgary, Alta.: University of Calgary Press. pp. 129–156. ISBN 978-1-55238-091-8.

50°26′53″N 104°36′53″W / 50.4480°N 104.61461°W / 50.4480; -104.61461