Resolution 7478 hazard mitigation

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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan Volume 2 — Hazard Inventory What is the coldest wind chill ever seen in the Twin Cities or Minnesota? The answer can be a little tricky because in November 2001 the formula on how to calculate the wind chill was changed. Perhaps the coldest wind chill the Twin Cities has ever seen was -67°F with the new formula (-87°F with the old formula) back on January 22, 1936. The temperature was -34°F with a wind speed of 20mph. All traffic in the Twin Cities was severely impacted and several fatalities were caused by the cold. Without a lengthy state-wide wind record, it is difficult to say when the coldest statewide wind chill was. There are some candidate dates though besides January 22, 1936. On January 9th and 10th, 1982 temperatures of -30°F and winds of around 40mph were reported in Northern Minnesota. This would translate to -71°F by the new formula (-100°F by the old formula.) A few other notable extreme cold events are: 1989 Feb 3: • At 6:00 AM in the Twin Cities the air temperature was -22°F with a wind speed of 17mph, creating a wind chill temperature of -49°F (by the 2001 formula). 1994 • On January 13, 1994, an arctic air mass settled over Hennepin County. From January 13 to January 19, true air temperatures dropped from -10°F on January 13 to -27°F on January 19. The high temperature on January 18 was -16°F. Morning air temperature readings were -26°F in the Twin Cities at gam with a wind chill temperature of -48°F (by the 2001 formula). The University of Minnesota on the Twin Cities campus closed on the 18th due to the cold and Governor Arne Carlson closed all public schools. 1996 • On January 31, 1996, some of the coldest weather to ever hit Hennepin County settled over the area and remained entrenched through February 4. Minneapolis set three new record low temperatures as well as Minnesota recording the coldest day on record on February 2. A mean temperature of -25°F was measured that day with a high of -17°F and a low of -32°F. This was within two degrees of tying the record low temperature set in the Twin Cities and the coldest temperature recorded this century. On the same date that the Minnesota state record minimum temperature record was set on February 2, 1996 (- 60°F near Tower), Governor Arne Carlson cancelled schools for cold a second time. In the Twin Cities at 6am February 2, 1996, the air temperature was -30°F with a wind chill temperature of -48°F (based on the 2001 formula). • Another extreme cold event took place on December 24, 1996. A strong low-pressure system that deposited heavy snow over northern Minnesota also brought down very cold Canadian air. Temperatures fell to 15 to 35 degrees below zero. In addition, the high temperature on Christmas Day in Minneapolis was only -9°F. Combined with the record low temperature that morning of -22°F, the mean temperature for Christmas Day was - 16°F. Christmas Day, 1996 set a record for being the coldest Christmas Day on record for the Twin Cities metro going back to when modern day records began in 1871. The temperature in Minneapolis fell to -27°F. 2004 • The first wind chill warning that was issued for the Twin Cities under the new wind chill temperature formula established in 2001 was the arctic outbreak of January 29-30, 2004. The coldest wind chill observed in the Twin Cities during that period was -430F at 8:00 AM on January 30, 2004. 163