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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />For instance, the six months from May through October of 2022 were the 41h driest on record in Hennepin <br />County, with the US Drought Monitor indicating Extreme Drought, the second -highest level, over much of <br />the county. A very wet period quickly followed it, however, and the six months from November through <br />April 2023 became the fourth wettest on record. Dry conditions set in again, with May through August <br />2023 ranking 3rd driest on record, followed by much -above -normal precipitation in September and <br />October, and then the third -wettest December on record. This oscillation between wet and dry regimes <br />is illustrated in GRAPHIC 4.3.11. <br />GRAPHIC 4.3.11 Sequential episodes of very dry and very wet conditions during 2022 and 2023 in <br />Hennepin County. Source: DNR Climate Trends (https://arcgis.dnr.state.mn.us/ewr/climatetrends/). <br />Recent Precipitation Departures from 1991-2020 Averages, and <br />Ranks from 1895 to 2023 Hennepin County <br />60% 54% 4th wettest <br />40 <br />a� <br />20% <br />0% <br />� -20 <br />0 <br />-40 <br />-60 <br />-80 <br />Humidity <br />-50% 4th driest -55% 3rd driest <br />June - October 2022 November 2022 - April May - August 2023 September - <br />2023 December 2023 <br />Increased humidity has been notable during all seasons in recent decades. From 2000 through 2023, the <br />Twin Cities long-term climate station measured more daily record -high and fewer daily record -low dew <br />point temperatures (a measure of humidity) than any other time since records began in late 1902. Of the <br />14 documented days with extreme humidity yielding at least one hourly 80' F dew point reading, 10 have <br />occurred since 1990, and none occurred prior to the 1960s. <br />Even though the highest air temperatures of summer and the number of 90' or 95' F days has not <br />increased over the long-term, extremely humid conditions have at times combined with hot air masses to <br />yield unprecedented Heat Index values, which measure what the air feels during heat waves. On July 19, <br />2011, Flying Cloud airport measured a Heat Index of 1227, while the Twin Cities airport measured 119'F. <br />On August 22, 2023, another intense heat wave fueled by high moisture and dew points, sent Heat Index <br />values into the upper 110s F across the county, with 120' F recorded at the Hennepin -West Mesonet <br />stations located in Hanover and at the MSP Airport. <br />Record humidity has not been confined to the summer, when it is most noticeable to humans, but in fact <br />53 <br />