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, 2017
What happened in August 2017:
- In August 2017, the state had above normal precipitation, with notable exceptions in the northwest and far southeast. The preliminary statewide precipitation total is 5.15 inches or 1.71 inches above the long term average. This is high enough to be the 11th wettest August on record statewide back to 1895. There was a very wide range in precipitation totals in the state, from over thirteen inches in the Redwood Falls area, to under an inch in the far southeast. Departure from normal ranged from two to six inches above normal for southwest, central and northeast Minnesota and two to three inches below normal in the northwest and southeast. Looking at the Meteorological Summer from June to August statewide average precipitation finished at 11.57 inches or .42 inches above normal. The last time there was an average statewide summer precipitation total below average was in 2013.
[see: August 2017 Precipitation Total Map | August 2017 Precipitation Departure Map | August 2017 Climate Summary Table | August 2017 Percent of Normal Precipitation Map]
- August 2017 saw two heavy rain events with the largest event occurring on August 16-17 affecting west central Minnesota. Some notable events of the month were:
- Heavy rains fell over southern and central Minnesota during the evening and overnight hours of August 13-14, 2017. A volunteer rain gauge reader near Montevideo in Chippewa County saw 3.96 inches of rain. Another observer near Glencoe reported torrential rains between 9:30 and 10:30pm in McLeod County and had a 24 hour total of 3.79 inches.
[see: Heavy Rain: August 13-14, 2017]
- The largest rain event for the month was on August 16-17. This event hit west central Minnesota the hardest, with many areas from southwest to northeast Minnesota receiving substantial rain. The largest official rainfall reports came from Redwood Falls, where the airport recorded 9.45 inches, and a volunteer with the National Weather Service's cooperative observer program reported 8.12 inches-- both in 24 hours. These were the highest 24 hour rainfall totals for a rain event since the 10.45 inches reported at Two Harbors for the June 20, 2012 northeast Minnesota flood. There was wind damage as well including eight short-lived and relatively weak tornadoes.
[see: Heavy Rain and Tornadoes: August 16-17, 2017]
- The preliminary statewide average temperature for August 2017 was 64.2 degrees or 2.1 degrees below average. August 2017 tied with 2009 as the 24th coolest August on record going back to 1895. The maximum temperatures were cooler compared to average than the minimum temperatures. The average maximum August 2017 temperatures were ranked as the 16th coolest on record. The warmest August maximum temperature found was 93 degrees on August 1 at Granite Falls, with the coldest minimum temperature of 30 degrees at Embarrass on August 24 and 25. Looking at the Meteorological Summer from June to August statewide average temperature was very close to the long term average at 66.2 degrees or one tenth of a degree below the long term average. This was the coolest summer since 2009.
[see: August 2017 Climate Summary Table | 2017 August Departure from Normal Temperature Map]
- In terms of mugginess, the summer of 2017 was below the level of recent years and was the least muggy summer back to 2009. Looking at the 6pm dew point temperature from June to August in the Twin Cities, the summer average was 56.2 degrees or 1.4 degrees below the long term average. The highest dew point temperature in the Twin Cities was 74 degrees during the evening of July 25. [see: Twin Cities Dew Point Temperature History]
Where we stand now:
- Seasonal precipitation totals(April 1 through September 5) ranked above the historical median over much of central and northeast Minnesota, with northwest Minnesota much below normal. The southern counties bordering Iowa were near normal.
[see: Seasonal Precipitation Ranking Map]
- The U. S. Drought Monitor map released on September 5, depicts 17 percent of the state in the Moderate Drought category, mostly in northwest and north central Minnesota and a small part of southeast Minnesota. This is about the same since early August. 25 percent of the state is in the Abnormally Dry category, a bit of a decrease since early August. Last year at this time there was only a small area of Abnormally Dry conditions in southwest Minnesota. 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 above normal stream discharge values in the northwest. The lowest values were found in the northwest with normal to below normal stream discharge values.
[see: USGS Stream Flow Conditions]
- Water levels on most Minnesota lakes vary depending on lake and location in the state. Mille Lacs was above the median lake level for August. On September 6, Minnetonka was at 929.29 with 150 cfs flowing through Grays Bay Dam. White Bear Lake was at 923.10 feet on September 7, a rise of .60 feet from one year ago and a rise of 4.26 feet from the record low of 918.84 measured January 10, 2013. Rainy and Lake of the Woods were in the median range for August. Lake Superior was at 603.02 feet on September 1, four 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 3 reports that topsoil moisture across Minnesota is 3 percent Very Short, 15 percent Short, 76 percent Adequate, and 6 percent Surplus. Soil moisture levels at Lamberton is above the historical median on September 1 and is now 1.41 inches above the historical average. The largest change from a month ago has been a recharge of soil moisture for the top eighteen inches.
[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 Minnesota, except for northwest sections where the fire danger is High. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]
- The September precipitation outlook leans towards below normal precipitation across the entire state with the best chances in southwest Minnesota. September precipitation normals 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 leans towards equal chances for below, above normal temperatures throughout Minnesota, with a slight tendency for below normal temperatures in far southeast Minnesota and above normal temperatures in northwest Minnesota. 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 equal chances below-normal, near-normal, or above-normal temperatures and 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:
- A new tool has just been launched by the State Climatology Office that shows normal temperature and precipitation for various locations across the state. [see: Climograph Portal]