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 6, 2023
What happened in September 2023:
- Much of Minnesota had dry conditions for the first three weeks of September 2023, except for northeast Minnesota. A widespread rain event hit the state for the final days of the month and elevated the statewide average to just above normal. The preliminary average for Minnesota was 3.50 inches or .27 inches above normal, much wetter than September 2022 that was almost two inches below normal. One of the wettest locations for September 2023 was Duluth, which finished 10.36 inches or 6.88 inches above normal. It was the 2nd wettest September on record for Duluth, with the wettest September in 1881 with 11.52 inches. The driest location in the state found so far was Lamberton in Redwood County with only .60 inches or 2.86 inches below normal. Sioux Falls, SD had .51 inches or 2.22 inches below normal.
[see: September 2023 Precipitation Total Map | September 2023 Precipitation Departure Map | September 2023 Climate Summary Table | 2023 September Departure from Normal Precipitation Map
- September 2023 had two main rain events of note for the month. Duluth saw heavy rain on September 5 and there was a much larger event across a good chunk of the state on September 23-25.
- A meandering cut-off low pressure system brought beneficial rains over eastern and west central Minnesota, where many rainfall totals over the 72 hour period ending Monday, September 25th were two inches or more. The normal monthly September rainfall is around three inches in Minnesota. Long term deficits remain over may parts of the state so there’s a long way to go to eliminate the drought. The Twin Cities saw one to four inches of rain from this event, with Hennepin County seeing the most. The Chanhassen National Weather Service Office saw 3.26 inches for a two-day total. The Duluth International Airport on September 24th saw 3.02 inches of rain.
[see: Welcome Rains Douse Minnesota: September 23-25, 2023]
- Not only was September 2023 yet another month in a row with above normal temperatures, but it was likely one of the top five warmest Septembers on record statewide. In the Twin Cities, it was the warmest September on record. The preliminary average statewide temperature was 4.8 degrees above normal. The warmest temperature found in the state so far was 103 degrees F at Canby in Yellow Medicine County on the 4th (reported on the 5th). The coldest temperature was 27 degrees at Hibbing in St Louis County on the 13th. No widespread killing frost was reported in Minnesota during the month of September.
[see: September 2023 Climate Summary Table | 2023 September Departure from Normal Temperature Map]
Where we stand now:
- Seasonal precipitation totals (April 1 through October 3) ranked below the historical median for the majority of the state, with some exceptions. The driest areas were in southwestern Minnesota and along the Iowa border where some areas were less than the second percentile, about a 1 in 50 year occurrence. A small area around Duluth and some localized spots in Nicollet and Brown Counties were in the 70th percentile.
[see: Seasonal Precipitation Ranking Maps]
- The U. S. Drought Monitor map released on October 5, depicts drought intensity that has decreased over the last couple weeks. 18% of the state in the Abnormally Dry category, 38% in the Moderate Drought category, 36% in the Severe Drought category and 8% in the Extreme 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 levels have rebounded over the last two weeks in the state. On October 5, Stream flows are generally normal to below normal in the state with some exceptions. Stream flows are low on the Sauk River at St. Cloud and well below normal at High Island Creek near Henderson. The St. Louis River at Scanlon was above normal and the Middle River at Argyle was much above normal.
[see: USGS Stream Flow Conditions | Weekly Stream Flow Maps and Tables]
- Water levels fell on lakes in general during the summer and into autumn. Mille Lacs was about three-tenths of a foot below the median lake level for early October. On October 5, Minnetonka was at 928.24 feet, about four-tenths of a foot higher than this time last year. White Bear Lake was at 922.25 feet on October 5, a fall of about three tenths of a foot from one year ago. Rainy Lake was in the normal band for the time of year and Lake of the Woods was just below the normal band for early October. Lake Superior was at 602.40 feet on Sept 29, three inches higher than the average late September level. Superior is forecasted to fall two inches by the end of October.
[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 1 reports that topsoil moisture across Minnesota is 20 percent Very Short, 44 percent Short, 35 percent Adequate, and 1 percent Surplus. 90% of the corn crop was mature, and about 20% was harvested for grain, about a week ahead the five year average. 33% of soybeans were harvested, very near the five year average. Lamberton in Redwood County missed out on much of the September rains and soil moisture levels there for October 1 are the lowest for the date compared to the last four years. Soil moisture levels at Lamberton are about 2.93 inches short of the historic average. There is virtually no moisture in the top two feet of the profile.
[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 5 rated by DNR Forestry as Low across southern Minnesota and northern St. Louis and Lake Counties, Moderate across the rest of northern and central Minnesota. Historically, 80 percent of all wildfires in Minnesota occur during April and May.
[see: Fire Danger Rating Map]
- The Climate Prediction Center's outlook has a tendency for above normal temperatures for October, with equal chances for below, normal, and above normal precipitation. 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, and much of the country as well. In Minnesota, 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]
- According to the September El Niño-Southern Oscillation (ENSO) Outlook, there is a greater than a 95% of El Niño from January-March 2024. There is also a 71% chance that there could be a strong El Niño this winter (Oceanic Niño Index ≥ 1.5 ˚Celsius). The Outlook for December 2023-February 2024 has a fairly strong tilt for above normal temperatures in Minnesota.
[see: Climate Prediction Center December-January 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:
- For the third year in a row, a there was a significant drought in Minnesota. The epicenter of the drought of 2021 was in the north, in 2022 it was in the south and in 2023, the drought was more general throughout the state, with the exception of the northeast. This will likely be the fourth year in a row where the Twin Cities precipitation total will fall below the normal annual precipitation of 31.62.
Upcoming dates of note:
- October 19: National Weather Service releases 30/90 day temperature and precipitation outlooks
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Pete Boulay, DNR Climatologist