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: October 12, 2021
What happened in September 2021:
- September 2021 finished below normal for precipitation statewide, but varied greatly in the state. The preliminary average for Minnesota was 2.77 inches or .57 inches below normal. September was dry on the northwest and quite dry in the southeast, with a swath from southwest and west central Minnesota to east central Minnesota that was above normal. One of the driest locations in the state was Caledonia in Houston County which saw 1.09 inches of precipitation for the month or 2.95 inches below normal. One of the wettest locations was Madison in southwest Minnesota that finished with 5.74 inches or 3.10 inches above normal.
[see: September 2021 Precipitation Total Map | September 2021 Precipitation Departure Map | September 2021 Climate Summary Table | 2021 September Departure from Normal Precipitation Map - September 2021 had one severe storm episode of note for the month:
- A line of severe thunderstorms moved across southern Minnesota on September 17. While the wain was welcome, the storms also spawned four weak tornadoes in the southern Twin Cities Metro area.
[see: Summary of September 17, 2021 Preliminary Survey Results] - September continued the warm streak of months that began in March 2021 and finished well above normal statewide. The preliminary average statewide temperature is 2.7 degrees above normal. The warmest temperature found in the state so far was at Milan in Chippewa County with 95 degrees on September 16. The coldest temperature was 29 degrees at multiple stations and multiple dates in northeast Minnesota. There has been no widespread frost in central and southern Minnesota through October 11. In addition, many locations in northern Minnesota have yet to see a killing frost.
[see: September 2021 Climate Summary Table | 2021 August Departure from Normal Temperature Map]
Where we stand now:
- Seasonal precipitation totals (April 1 through October 5) ranked above the historical median over the southeast and parts of the west central. Most of the rest of the state is ranked below the 40th percentile. South central and a large part of northern Minnesota is ranked in the 20th percentile or less.
[see: Seasonal Precipitation Ranking Maps] - The U. S. Drought Monitor map released on October 7, depicts areas of drought that have been reduced in intensity since last month. 9.8% of the state is free of any drought. 23% of the state in the Abnormally Dry category, 19% in the Moderate Drought category, 31% in the Severe Drought category and 18% in the Extreme Drought category. The Exceptional Drought intensity was reported from August 10 through September 14. 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 levels have improved over the past month in nearly all but the far north central. Stream flows are generally normal to below normal in the state with some exceptions. Stream flows in west central Minnesota are above normal, much above normal and even high in northern Lac Qui Parle County. There are much below normal stream flows in north central and northeast Minnesota.
[see: USGS Stream Flow Conditions | Weekly Stream Flow Maps and Tables] - Water levels on most Minnesota have stabilized some over the past month. Mille Lacs was about a half foot below median lake level for early October. On October 7, Minnetonka was at 928.23 feet and the Grays Bay Dam has been closed since July 14. The lowest that Minnetonka has reached so far in this drought was 928.18 during the third week of August. White Bear Lake was at 923.49 feet on October 11, a fall of about eight tenths of a foot from one year ago. Rainy Lake continued to be below the normal band for October and Lake of the Woods was below the 10th percentile for early October. Lake Superior was at 602.03 feet on October 8, one inch lower than the average October level and ten inches lower than the water level from October 8, 2020.
[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 October 4 reports that topsoil moisture across Minnesota is 7 percent Very Short, 24 percent Short, 67 percent Adequate, and 2 percent Surplus. 90% of the corn crop was mature, two days ahead of last year, but eleven days ahead of the 5-year average. Maturity of corn was two weeks ahead of the five year average and three weeks ahead of last year. 62% of soybeans were harvested, two days ahead of last year and two weeks ahead of average. Soil moisture levels at Lamberton recovered greatly since mid-august and on October 1, soil moisture is above the historic average by an inch and a half.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research and Outreach Center (Lamberton) | U. of M. Southern Research and Outreach Center (Waseca)] - The potential for wildfires as of October 11 rated by DNR Forestry as Low across the entire state Minnesota. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]
Future prospects:
- It looks like the seven month warm pattern will continue for October, with the recent trend of wetter conditions continuing. The October precipitation outlook leans towards above normal precipitation across the entire state, especially in the southwest. October precipitation normals range from about one-and-a-half inches in northwest Minnesota to about three-and-a-half inches in Cook County. Southern and central Minnesota range by about one-and-three-quarters of an inch in the southwest to about two-and-a-half inches in east central Minnesota.
[see: Climate Prediction Center 30-day Outlook | October Precipitation Normal Map] - The October temperature outlook has a strong tendency for above normal temperatures throughout Minnesota for October. Normal October high temperatures are in the 60s to start the month, dropping to the low 50s to upper 40s by month's end. Normal lows are in the 40s early in the month, falling to the 30s by late October.
[see: Climate Prediction Center 30-day Outlook | October Temperature Normal Map] - The 90-day temperature outlook for October through December has a three-sided coin of equal chances of above, normal and below normal temperatures. The 90-day precipitation outlook for October through December indicates equal chances of below-normal, near-normal, or above-normal conditions across most of Minnesota.
[see: Climate Prediction Center 90-day 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:
- The statewide average temperature of the first eleven days of October are about twelve degrees above normal. as of October 11, there hasn’t been a temperature of 32 degrees or colder at International Falls and many locations in the north. This is beginning to set records for the latest first frost. The previous latest date of the first frost in International Falls was October 8, 2016. Continuous records begin for International Falls begin in 1947. Cloquet’s previous record was October 9, 2016. The latest first frost at Grand Rapids is October 13, 2016.
Upcoming dates of note:
- October 21: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist