HydroClim Minnesota for Early September 2019

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 6, 2019

What happened in August 2019:

  • Precipitation was highly variable across the state in August 2019, depending upon where the thunderstorms fell. There were pockets that had well above normal precipitation such as Cass Lake in the north central with 4.99 inches or 2.02 above normal. Morris in west central Minnesota finished with 5.53 inches or 2.20 inches above normal. One of the wettest locations in the state was Stillwater in east central Minnesota that had 7.96 inches or 3.15 inches above normal. On the other end of the spectrum was the station 7 miles northwest of Two Harbors that finished with 1.99 inches or 1.75 inches short of normal and Rochester with 1.54 inches for August 2019 or 2.98 inches behind normal. Rochester has been very wet this year and August was the first month since March that was below normal. The preliminary statewide average was 3.25 inches or .67 inches below normal. The Twin Cities finished with the 20th wettest summer (June-August) on record (1871-2019) with 15.48 inches or 2.89 inches above normal.
    [see: August 2019 Precipitation Total Map  | August 2019 Precipitation Departure Map  | August 2019 Climate Summary Table  |  August 2019 Percent of Normal Precipitation Map]
  • There were two severe storm events of note in August 2019. Large hail hit the northwest suburbs of the Twin Cities on August 5 and on August 26 saw tornadoes and a waterspout.
  • Thunderstorms during the morning of August 5 moved through northern portions of Minnesota, with heavy rains and strong winds that blew down trees and power lines. Damage was reported near Walker, and also in and around Duluth, where the International Airport recorded a 61 mph wind gust. The airport at Hinckley recorded a 62 mph wind gust as well. In the early afternoon, storms redeveloped and moved into the northwest suburbs of the Twin Cities. One cell in particular had a 1-3 mile-wide core of damaging hail that dented cars, broke windows, and banged on roofs and siding across the western, northwestern, northern, and northeastern Twin Cities suburbs. Hail the size of grapefruits (four inches in diameter) was documented and reported around Delano in Wright County.
    [see: Large Hail: August 5, 2019]
  • Small, but potent thunderstorms caused tornadoes and a waterspout during the evening of August 26. At around noon, there was a large band of moderate to heavy rain marching eastward across Minnesota ahead of a cold front. As the rain moved off to the east, some sunshine appeared and a broken line of thunderstorms rapidly developed behind the main area of rain. Some of the cells were strong enough to produce tornadoes and a waterspout. The waterspout was seen by many over Farm Island Lake in Aitkin County. This caused dock, boat and tree damage. Two tornadoes were surveyed in Mille Lacs County: an EF-0 tornado north of Milaca and an EF-1 south of town. The tornadoes caused damage to sheds, shingles, a chicken coop and at least one hapless trampoline.
    [see: Tornadoes and a Waterspout: August 26, 2019]
  • August 2019 finished cooler than normal for many locations with the statewide average temperature about 1.6 degrees below normal. The temperatures were rather pleasant for the month and was one reason the Minnesota State Fair set an attendance record. Hot days were scarce. The warmest temperature found was 94 degrees at St. James on August 4. The coldest minimum temperature was 34 degrees at Goodridge in northwest Minnesota on August 30. While the meteorological (June-August) summer did finish above normal in the Twin Cities, there were relatively few days of 90 degree or greater maximum temperatures. Barring any late season warm spell, the count for 2019 will be 4. The last time there were only 4 days of 90 plus highs in a year was 2015. In 2018 there were 20.
    [see: August 2019 Climate Summary Table  |  2019 August Departure from Normal Temperature Map]

Where we stand now:

  • Seasonal precipitation totals (April 1 through September 3) ranked above the historical median over southern and central and parts of north central Minnesota. Most of the rest of northern Minnesota was normal to below normal for the period. The largest deficit being in St. Louis County.
    [see: Seasonal Precipitation Ranking Map]
  • The U. S. Drought Monitor map released on September 5, depicts 9.8 percent of the state in the Abnormally Dry category, confined to northwest Minnesota. One year ago, 27 percent of the state had Abnormally Dry conditions and 7 percent of the state 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 much above normal across large sections of central and southern Minnesota, with normal to below normal stream discharge values in the north. The lowest percentage of normal found in the state on September 5 was in the north central on the Littlefork River in Koochiching County with streamflow at the 24th percentile.
    [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. On September 5, Mille Lacs was about a half foot lower than it was in July. Minnetonka was at 929.30 feet with 150 cfs flowing through Grays Bay Dam. White Bear Lake was at 925.00 feet on September 5, a rise of 1.24 feet from one year ago and a rise of 6.16 feet from the record low of 918.84 measured January 10, 2013. Rainy Lake and Lake of the Woods were in the median range for early September. Lake Superior was forecasted to be at 603.18 feet on August 30, twelve inches higher than the monthly average for late August and ties the record high level for August set in 1952.
    [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 September 4 reports that topsoil moisture across Minnesota is 1 percent Very Short, 13 percent Short, 79 percent Adequate, and 7 percent Surplus. Soil moisture levels at Lamberton were above the historical median on September 1 and were now 1.60 inches above the historical average. Soil moisture levels at Lamberton have been above the median for the entire growing season and on September 1, there is about a half 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. Historically, 80 percent of all wildfires in Minnesota occur during April and May. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
    [see: Fire Danger Rating Map]

Future prospects:

  • The September precipitation outlook leans towards above normal precipitation across the entire state. The best chances for a wetter September are in central and northern Minnesota. 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 has a fairly strong tendency for below normal temperatures across the entire state. 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 a tendency for above normal precipitation for Minnesota, especially in northwest parts of the state. The September through November temperature projection also offers a tendency for above-normal conditions statewide as well as the lower 48 states and Alaska.
    [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. Will this precipitation be rain or snow? Time will tell!
    [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:

  • There was a record number of beach closures in Minneapolis for the summer of 2019. However, records for the beach sampling program of the Minneapolis Park and Recreation Board only go back to 2003. Still, this is the most closures in at least sixteen years. The blame was placed on heavy summer rains washing contaminants into the lakes. [see: Closed Beaches in 2019]

Upcoming dates of note:


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Pete Boulay, DNR Climatologist

  • September 19: National Weather Service releases 30/90 day temperature and precipitation outlooks

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