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 5, 2024
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distributed: September 5, 2024
What happened in August 2024:
- The wet year of 2024 continued into August, but it was not universal. While a large swath of central, parts of northwest and southeast Minnesota finished with above normal precipitation, large areas of northeast and southwest Minnesota fell a bit short. Stearns County to Isanti County were precipitation totals were two to three inches above normal. The wettest location found so far was at Collegeville with 8.16 inches of precipitation or 4.07 inches above normal. One of the drier locations was at Pipestone with 1.52 inches of precipitation or 1.94 inches short of normal. The preliminary statewide average precipitation was 4.20 inches or .59 inches above normal.
[see: August 2024 Precipitation Total Map | August 2024 Precipitation Departure Map | August 2024 Climate Summary Table | August 2024 Percent of Normal Precipitation Map] - There were two weather events of note in August 2024. The first was widespread soaking rains in central and southern Minnesota, with an outbreak of tornadoes affecting some communities in the far south-central part of the state. ;
[see: Heavy Rain and Tornadoes, August 5, 2024] - The second noteworthy event happened near the end of the month and had a high heat and humidity episode along with it. Two waves of severe thunderstorms affected parts of central and southern Minnesota Monday August 26 into Tuesday August 27, knocking down trees and knocking out power, with many areas hit equally hard by both waves. An extremely humid and very warm air mass overspread most of Minnesota on Monday, August 26. Stations across the state registered dew point temperatures in the middle to upper 70s F with some rare low 80s F dew points reported in southern parts of the state. Combined with temperatures in the 80s to low 90s F, the moisture drove Heat Index values to the 100-110 F range, especially in southern and eastern areas.;
[see: Humid Heat and Severe Weather Double-Header, August 26-27, 2024] - It will be a photo finish, but it appears as though that August will wind up slightly above normal for temperature, which would be the fifth August in a row that Minnesota finished with above normal temperatures. The preliminary average was 67.8 degrees or .3 degrees above normal. The highest air temperature found so far was 95 degrees at Austin, Rushford and Forest Lake during that high heat and humidity event of August 26. The lowest temperature of the month was at Brimson on August 6.
[see: Humid Heat and Severe Weather Double-Header, August 26-27, 2024] - [see: August 2024 Climate Summary Table | 2024 August Departure from Normal Temperature Map]
Where we stand now:
- Seasonal precipitation totals (April 1 through September 3) generally ranked well above the historical median, except for a few small areas of north central and northeast Minnesota. A large area of southern and central Minnesota are ranked in the 98th percentile for wetness.
[see: Seasonal Precipitation Ranking Map] - The U. S. Drought Monitor map released on August 27 depicts 12% of the state in the Abnormally Dry category. The state was free of any drought indicator from June 11 to August 13. Last year at this time, there was only 1% of the state that was free of any drought designation. 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 above to much above normal stream flows in the Minnesota, the Red River and the Mississippi River from the Twin Cities to Winona. There's mostly normal (the 25th to the 75th percentile) over northern and southern Minnesota, with the St. Louis River in the below normal percentile in the Duluth area. [see: Cooperative Stream Gauging | USGS Stream Flow Conditions]
- Water levels on Minnesota lakes vary depending on lake and location in the state. Mille Lacs on September 4 was at 11.33 feet, about a tenth of a foot above the median. On September 4, Minnetonka was at 929.29 feet, about 1.37 feet higher than this time last year.. On September 4, White Bear Lake was at 923.13 feet, about a foot higher than last year at this time. The level of Lake of the Woods is in the median band, with a downward trend. Rainy Lake right in the middle of the median band. Lake Superior was forecasted to be at 602.03 feet, unchanged since July 30. The lake level in Superior is forecast for a slow fall over the next month.
[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 1 percent Very Short, 11 percent Short, 77 percent Adequate, and 11 percent Surplus. Available soil water at Lamberton on August 15 was approximately 6.62 inches, 2.47 inches above normal. There’s been a surplus of moisture at Lamberton all during the growing season.
[see: Agricultural Statistics Service Crop Progress and Condition | U. of M. Southwest Research & Outreach Center (Lamberton)] - The potential for wildfires rated by DNR Forestry on September 4, as Low across the entire state except in far northwest Minnesota, where a Moderate potential exists. 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 across 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 has a strong tendency for above normal temperatures. In the Twin Cities, ten of the last twelve Septembers from 2012 to 2023 were above normal for average temperature. 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 across the state. The September through November temperature projection offers a tendency for above-normal conditions statewide.
[see: Climate Prediction Center 90-day Outlook] - The Winter Outlook (December-February) from the Climate Prediction Center depicts a slight tendency for below normal temperatures over northwest Minnesota with equal chances of below normal and above normal temperatures across the rest of the state. There is a slight tilt for above normal precipitation across the eastern half of the state. La Niña is expected to be present this winter.
[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:
- It has been a fairly quiet tornado season so far in Minnesota with a preliminary total of 36 fairly weak tornadoes as of September 4. The 1991-2020 average in Minnesota for a season is 46. In 2023, there were 25. For comparison, Iowa has had a preliminary total of 113 tornadoes so far in 2024.
Upcoming dates of note:
- September 19: National Weather Service releases 30/90 day temperature and precipitation outlooks
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