4.7 SR 06-01-2020 - Laserfiche WebLink

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Sherburne County Multi -Hazard Mitigation Plan, 2020 According to the 203.5 Minnesota Weather Almanac, During the three most recent decades, the Minnesota climate has shown some very significant trends, all of which have had many observable impacts... Among the detectable measured quantity changes are: (1) warmer temperatures, especially daily minimum temperatures, more weighted to winter than any other season; (2) increased frequency of high dew points, especially notable in mid- to late summer as they push the Heat Index values beyond zoo°F; and (3) greater annual precipitation, with a profound increase in the contribution from intense thunderstorms (Seeley M. , 2oi5). Temperature and precipitation projections below are taken from the Minnesota Department of Health Region 6 profile. Appendix L provides the full MDH profile for Region 6, which includes Sherburne County. The information in this report was used to help inform the updated risk assessments in Section 4 — Risk Assessment of this plan for natural hazards and their relationship to climate change. Temperature There has been an increase in winter and summer temperatures. Our average winter lows are rising rapidly, and our coldest days of winter are now warmer than we have ever recorded. In fact, Minnesota winters are warming nearly 13 times faster than our summers. The continued rise in winter temperatures will result in less snow pack, which will increase chances for grassland/wildfires as well as drought. The warmer winter temperatures will also have major consequences for our ecosystems, including native and invasive species, whose growth, migration, and reproduction are tied to climate cues. The increase in Lyme disease across Minnesota is also likely influenced in part by the loss of our historical winters, due to a longer life -cycle period for ticks. Freeze -thaw cycles are likely to increase as well, damaging roads, power lines and infrastructure, and causing hazardous travel conditions. By mid-century our average summer highs will also see a substantial rise, coupled with an increase in more severe, prolonged heat waves that can contribute to drought and wildfires and pose a serious health threat, particularly to children and seniors (MDH, 2o3.8). Precipitation There has been an increase in total average as well as heavy precipitation events, with longer periods of intervening dry spells. Our historical rainfall patterns have changed substantially, giving rise to larger, more frequent heavy downpours. Minnesota's high -density rain gauge network has captured a nearly four fold increase in "mega -rain" eventsjust since the year 2000, compared to the previous three decades. Extreme rainfall events increase the probability of disaster -level flooding and new research suggests a recent increase in precipitation -triggered landslide activity in the metro region. However, there is also an increased probability that by mid-century heavy downpours will be separated in time by longer dry spells, particularly during the late growing season. Over the past century, the Midwest hasn't experienced a significant change in drought duration. However, the average number of days without precipitation is projected to increase in the future, leading Minnesota climate experts to state with moderate -to-high confidence that drought severity, coverage, and duration are likely to increase in the state. Modeling future precipitation Page122