HydroClim Minnesota for Early September 2018

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 7, 2018

What happened in August 2018:

  • In August 2018, precipitation was highly variable across the state, depending upon where the thunderstorms fell. There were three main areas that finished well above normal: southwest, east central and especially far southeast, where some places had twice the amount of normal precipitation. The most rain fell in the far southeast corner, where Caledonia saw 11.17 inches or 6.15 inches above normal. One of the driest locations was near Tower in northeast Minnesota with 1.28 inches of rainfall for the month, or 2.55 inches below normal. The preliminary statewide average was 4.12 inches or .24 inches above normal. This was heavily weighted to the excessive precipitation totals in the southeast. Many locations elsewhere in the state saw below normal precipitation for the month.
    [see: August 2018 Precipitation Total Map  | August 2018 Precipitation Departure Map  | August 2018 Climate Summary Table  |  August 2018 Percent of Normal Precipitation Map ]
  • There were two heavy rain events of note in August 2018. Heavy rains fell on August 3 and another event was from August 24-28.
  • August 3 saw heavy rains and a tornado. The tornado began in Kandiyohi County and moved to the east, dissipating northwest of Litchfield in Meeker County There was some welcome rain for dry lawns in the Twin Cities. Heavier rain fell in the St. Cloud area with two to four inches of rain just north of St. Cloud. A CoCoRaHS observer in Foley reported 3.80 inches. Sartell saw 3.45 inches. A location west of St. Cloud saw 2.43 inches and there were reports of street flooding. The Twin Cities International Airport saw 1.02 inches of welcome precipitation.
    [see: Strong Thunderstorms and a Weak Tornado: August 3, 2018]
  • August 24-28, 2018 was a stormy period in Minnesota with tornadoes, hail and flooding affecting various parts of the state. Heavy rains fell over east central and southeast Minnesota on August 27, especially in Kanabec and Pine County with amounts of 2-3 inches reported. Rains were more intense in far southeast Minnesota. Houston County was hit the hardest. The highest total found was 8.63 inches in 24 hours from a MNgage observer located in Brownsville along the Mississippi River. In Houston County, an area of approximately nine townships or 324 square miles had six inches of rainfall in a 24-hour period.
    [see: Severe Storms and Flooding Rains: August 24-28, 2018]
  • August 2018 finished warmer than normal for many locations with the statewide average temperature about a half degree above normal. The warmest temperature found was 96 degrees at Argyle and Warren in northwest Minnesota on August 13 and the coldest minimum temperature was 32 degrees at Goodridge in northwest Minnesota on August 2. The Twin Cities finished with the 15th warmest summer (June-August) on record (1871-2018). This was mainly driven due to the warm overnight minimum temperatures (second place behind 2010). The maximum temperature average finished 26th. Six of the top 15 warmest summers have been in the 2000’s. 2018 was the warmest summer since 2012.
    [see: August 2018 Climate Summary Table  |  2018 August Departure from Normal Temperature Map ]

Where we stand now:

  • Seasonal precipitation totals (April 1 through September 4) ranked above the historical median over southern, east central and parts of north central Minnesota. Some parts of southwest and southeast Minnesota were ranked nearly the wettest on record. Northwest Minnesota was well below normal for the period.
    [see: Seasonal Precipitation Ranking Map]
  • The U. S. Drought Monitor map released on September 6, depicts 7 percent of the state in the Moderate Drought category, confined to northwest Minnesota. One year ago, 17 percent of the state had Moderate Drought conditions. On September 6, 27 percent of the state is in the Abnormally Dry category, also a bit of a decrease since late August. 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 above 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 values were found in the north central near Lake of the Woods, and also on the Straight River near Park Rapids.
    [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 7, Minnetonka was at 928.79 feet with 12 cfs flowing through Grays Bay Dam. White Bear Lake was at 923.76 feet on September 9, a rise of .66 feet from one year ago and a rise of 4.92 feet from the record low of 918.84 measured January 10, 2013. Rainy Lake was in the median range for early September and Lake of the Woods was below the median range for early September. Lake Superior was at 602.69 feet on September 7, six inches higher than the monthly average for September.
    [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 5 percent Very Short, 15 percent Short, 70 percent Adequate, and 10 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 at or above the median for the entire growing season so far.
    [see: Agricultural Statistics Service Crop Progress and Condition  |  U. of M. Southwest Research & Outreach Center (Lamberton)]
  • The potential for wildfires is currently rated by DNR Forestry as Low across all but far northern Minnesota. In the far northwest sections the fire danger is High. North central and parts of northern St. Louis and Lake Counties have a Moderate fire danger rating. 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 except in the northwest. The best chances for a wetter September are in southeast Minnesota. With the early September storms bringing 4.88 inches to Caledonia, not another drop could fall for the rest of the month and Caledonia would still wind up being above normal. 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 slight tendency for above normal temperatures in Minnesota except for the northwest part of the state where there are equal chances for above, normal and below normal temperatures. 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 equal chances of below-normal, near-normal, or above-normal conditions across most of Minnesota, with the September through November temperature projection also offers a fairly strong tendency for above-normal conditions statewide.
    [see: Climate Prediction Center 90-day Outlook]
  • The Winter Outlook (December-February) From the Climate Prediction Center has a strong tendency for above-normal temperature conditions statewide, especially in the north. Precipitation chances are a three-sided coin or equal chances for below-normal, near-normal, or above-normal precipitation for the Meteorological Winter from December-February.
    [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:

  • August 2018 might be most remembered for the persistent smoky skies during the first half of the month. The smoke originated from fires in Canada and gave the sky a milky appearance with reduced air quality. The smoke also suppressed the maximum temperature at times. [see: Smoky Skies]
  • While the temperature outlooks have a tendency for above normal temperatures for the rest of the year at most places, the growing season is over in International Falls. The minimum temperature there on September 6 was 28 degrees. This broke the old record of 33 degrees from 1956 and 1917. The normal low for the date at International Falls is 46.

Upcoming dates of note:


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Pete Boulay, DNR Climatologist

  • September 20: National Weather Service releases 30/90 day temperature and precipitation outlooks

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