HydroClim Minnesota for Early September 2020

HydroClim Minnesota for Early September 2020

A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of the month.

State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: September 4, 2020


What happened in August 2020:

  • August 2020 was a story of the haves and the have-nots with precipitation. The far southeast received scant precipitation for the month with spots in Houston County about four inches short of normal. On the other side of the spectrum, some locations in Clearwater, Hubbard, Cass and Itasca Counties saw a five to six inch surplus. Another pocket of excessive precipitation was in south central Minnesota over Nicollet and Sibley County. The highest preliminary monthly precipitation total found was 8.72 inches at Pokegama Dam in Itasca County, 5.22 inches above normal. The driest spot found was at Caledonia in southeast Minnesota with only .64 inches of precipitation or 4.38 inches below normal. The preliminary statewide average was 3.78 inches or 0.09 inches above normal.
    [see: August 2020 Precipitation Total Map  | August 2020 Precipitation Departure Map  | August 2020 Climate Summary Table  |  August 2020 Percent of Normal Precipitation Map]
  • There was one notable severe storm event in August 2020. Storms brought tornadoes, wind damage and flooding across central and northern Minnesota on August 14, 2020.
    [see: Tornadoes, Wind Damage and Flooding: August 14, 2020]
  • August 2020 was the third month in a row to finish with average temperatures above normal. The preliminary statewide average was 1.3 degrees above normal. There were many warm days and some muggy stretches as well. The highest temperature found so far for August 2020 was 97 degrees at Marshall in southwest Minnesota on August 24 and the coldest temperature was 36 degrees at Brimson in northeast Minnesota on August 30. The meteorological (June-August) summer finished in the top 20 warmest for many locations in the state, including the second warmest at Duluth. Only the summer of 2012 was warmer. For the Twin Cities it was a four-way tie for the 12th warmest. There were fifteen days of 90 or above for a maximum temperature. Last year there were only four days of 90 or above and in 2018 there were 20.
    [see: August 2020 Climate Summary Table  |  2020 August Departure from Normal Temperature Map]

Where we stand now:

  • Seasonal precipitation totals (April 1 through September 1) ranked above the historical median over much of northwest, north central and south central Minnesota, with areas below the historical median over central, far south, and northeast Minnesota.
    [see: Seasonal Precipitation Ranking Map]
  • The U. S. Drought Monitor map released on September 3, depicts 18.8 percent of the state in the Abnormally Dry category, confined to mostly northeast and southwest Minnesota, with another pocket in the southeast. Eight percent of the state is in the Moderate Drought category. The U.S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc.) are based on several indicators.
    [see: Drought Conditions Overview]
  • The U.S. Geological Survey reports that stream discharge values are normal to above normal across much of the state, with much above normal flow conditions in the Red River Valley. Northeast Minnesota has generally normal to below normal streamflow conditions.
    [see: USGS Stream Flow Conditions]
  • Water levels on most Minnesota lakes vary depending on lake and location in the state. Mille Lacs was about a half a foot above the median lake level for early September. Minnetonka was at 929.03 feet with 20 cfs flowing through Grays Bay Dam on September 2. White Bear Lake was at 924.60 feet on September 4, a fall of four tenths (.4) of a foot from one year ago. Rainy Lake was in the median range for early September and Lake of the Woods was below median range for early September and has been blow the median range since early June. Lake Superior was forecasted to be at 603.02 feet on August 28, ten inches higher than the monthly average for late August and two inches lower than in late August 2019.
    [see: Mille Lacs Lake Water Level  |  Lake Minnetonka Water Level  |  White Bear Lake Water Level  |  Lake of the Woods Control Board Basin Data  |  Corps of Engineers Great Lakes Water Levels]
  • The Agricultural Statistics Service on August 31 reports that topsoil moisture across Minnesota is 3percent Very Short, 11 percent Short, 77 percent Adequate, and 9 percent Surplus. Soil moisture levels at Lamberton have been above the median since July 15 and on September 1, there is around an inch of surplus moisture.
    [see: Agricultural Statistics Service Crop Progress and Condition  |  U. of M. Southwest Research & Outreach Center (Lamberton)]
  • On September 5, the potential for wildfires is currently rated by DNR Forestry as Low across the entire state, except for moderate fire danger over the northwest and Crow Wing and Cass County. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
    [see: Fire Danger Rating Map]

Future prospects:

  • The September precipitation outlook has a fairly strong tendency for below normal precipitation, especially in the western half of the state. September precipitation normal values range from about one-and-a-half inches in northwest Minnesota to about four inches in northeast and southeastern counties.
    [see: Climate Prediction Center 30-day Outlook  |  September Precipitation Normal Map]
  • The September temperature outlook also has a fairly strong tendency for below normal temperatures across the entire state, especially in the south. In 2019 the outlook was also for a cool September and the statewide average wound up to be two degrees above normal. Normal September high temperatures are in the middle to upper 70's degrees to start the month, dropping to the low to mid 60's by month's end. Normal lows are in the 50's early in the month, falling to the middle 30's to mid-40s by late September.
    [see: Climate Prediction Center 30-day Outlook  | September Temperature Normal Map]
  • The 90-day precipitation outlook for September through November indicates an equal chance for above, below and normal precipitation. The September through November temperature projection offers a tendency for above-normal conditions statewide as well as the lower 48 states and Alaska. Note that this was the same outlook as in September-November 2019 and the statewide average temperature for September-November wound up being a degree below normal!
    [see: Climate Prediction Center 90-day Outlook]
  • The Winter Outlook (December-February) from the Climate Prediction Center depicts equal chances for below-normal, near-normal, or above-normal temperature conditions statewide. Precipitation chances have a fairly strong tendency for above normal precipitation in the state for the Meteorological Winter from December-February. This was the same outlook as last year. The statewide average temperature for December 2019-February 2020 wound up being very close to normal and precipitation was about a half inch above normal. Will the Climate Prediction Center be correct again? Stay tuned!
    [see: Climate Prediction Center 3.5 month Outlook]
  • The National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products address both high flow and low flow probabilities.
    [see: National Weather Service - North Central River Forecast Center]

From the author:

  • How muggy was it this past summer? Looking at the counts of hourly 70 degree dew point temperatures or higher in the Twin Cities, the tally for 2020 was approximately 312 hours. This was short of the record of 512 hours in 2002, but still well above the 1891-2010 average of 182 hours. The last time there was this many hours of 70 or higher dew point temperatures in the Twin Cities was in 2018 with 347 hours. There were only 156 hours in 2019. So 2020 was muggier than average, but not a record.

Upcoming dates of note:

  • September 17: National Weather Service releases 30/90 day temperature and precipitation outlooks

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Pete Boulay, DNR Climatologist