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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />• Bouts of extreme cold in Hennepin County and throughout Minnesota and the region are now at <br />an all-time low in terms of both frequency and severity. Of all changes, the loss of cold weather <br />extremes has the strongest link with climate change. <br />• Extreme rainfall episodes have become both more intense and more frequent, and Minnesota <br />has seen seven "mega -rainfall" events since the year 2000. Changes in extreme rainfall behaviors <br />are strongly linked to climate change. <br />• A general increase in annual and seasonal snowfall has been punctuated by an uptick in the size <br />and frequency of large snowfall events. This is likely related to the presence of warmer air and <br />more water vapor during winter, which provides more energy to passing low pressure systems <br />capable of producing snow. <br />• Severe thunderstorms and tornadoes pose challenges to long-term analyses because of changes <br />in reporting procedures and detection technologies over time. That said, Minnesota has been in <br />a pronounced severe weather lull since the summer of 2011, which followed a very active spring <br />and record -setting year for tornadoes in 2010. Confidence in the link between climate change and <br />observed severe weather trends is low. However, the severe weather season has expanded <br />aggressively in recent years, with record -early tornadoes in Minnesota on March 6, 2017, and <br />record late tornadoes (by 30 days) on December 15, 2021. <br />• Humid heat waves have increased in severity and frequency, in response to higher humidity. <br />Summertime high temperatures and the number of hot days has not changed yet. <br />• Despite three straight years of significant growing season drought in 2021-2023, Hennepin County <br />still does not have a long-term trend towards increased drought frequency or severity. <br />These are just some examples of the effects of climate change in Hennepin County. <br />4.3.1.8. Future trends/likelihood of occurrence Ble <br />Projections of future climates from multiple sources indicate that the area is likely to continue to see a <br />rapid erosion of winter extreme cold temperatures, and it is expected that Hennepin County will fail to <br />reach previously common benchmarks by increasingly large margins. <br />Extreme rainfall is projected to increase, but it should not be expected to do so on a year -after -year basis. <br />Instead, climate change is increasing the long-term frequency and magnitude of these events, meaning <br />that storms of a certain size may come every 10-20 years instead of every 50 years. By mid-century, the <br />area should receive an additional 3-8 days per decade with rainfall in the top 2% of the historical <br />distribution (GRAPHIC 4.3.1J). Thus, the expectation is that unprecedented rainfall events will occur at <br />some point this century, but their likelihood in the next decade will be limited by their overall statistical <br />rareness. <br />GRAPHIC 4.3.1J Average difference in number of days per year by mid-century (2040-2070) with rainfall <br />in upper 2% of distribution. <br />58 <br />