A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the first Thursday of each month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
distributed: October 4, 2012
What happened in September 2012:
- Without exception, September 2012 monthly precipitation totals were very low across Minnesota. September rainfall totaled less than one inch in most locations, and less than one-half inch in numerous locales. The monthly precipitation totals fell short of the September average by two to three inches statewide. Preliminary data indicate that the state-averaged September 2012 precipitation total is either the driest or second driest in Minnesota's climate record.
- Monthly mean temperatures for September 2012 were very close to historical averages throughout Minnesota. Warmer than average days were offset by cooler than average nights. Large spreads between daytime and nighttime temperatures are common during spells of very dry weather. Extreme temperature values for September ranged from a high of 98 degrees F at Brownton (McCleod County) on the 11th; to a low of 16 degrees F at Warroad (Roseau County) on the 21st. Killing frosts occurred nearly everywhere in Minnesota in September. However, crops had reached full maturity and suffered little or no damage.
Where we stand now:
- The U. S. Drought Monitor, released on October 4, places portions of northwestern, southwestern, and south central Minnesota in the Extreme Drought category. Most of the rest of the state is depicted as undergoing Severe Drought or Moderate Drought. In total, 96 percent of Minnesota's landscape is considered to be in Moderate Drought or worse. The drought situation in northwest Minnesota and in far southeast Minnesota is the result of an historically dry autumn in 2011, a snow-sparse winter, and a dry 2012 growing season. The moisture deficits in southern Minnesota developed rapidly due to very hot and very dry conditions that began in mid-June and continued into the autumn. Extraordinarily dry conditions during the months of August and September 2012 caused rapid drought development in areas of Minnesota previously outside of the most intense drought regions. For those areas already undergoing significant drought, the late-summer/early-autumn extreme dryness exaggerated pre-existing conditions. Many Minnesota locales reported less than one and one-half inch of rainfall over the August plus September period. For large portions of Minnesota, August-plus-September 2012 rainfall totals rank at or below the lowest on record. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc) are based on several indicators.
- The U.S. Geological Survey and Minnesota DNR report that stream discharge values are extremely low at numerous Minnesota reporting locations. Many stream flow values rank below the 10th percentile when compared with historical data for this time of year.
- Water levels on many Minnesota lakes are very low in response to the dry, hot summer and early autumn. Lake Superior water level is similar to the 2011 level at this time of year, but well below the long-term average for the date.
- In their October 1 report, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 44% Very Short, 41% Short, 15% Adequate, and 0% Surplus across Minnesota. This represents a significant degradation in conditions when compared with an early-June soil moisture survey reporting only 5% of the landscape Short or Very Short. Soil moisture measurements made in late September at University of Minnesota Research and Outreach Centers indicate extraordinarily dry conditions in the soil profile. Soil moisture content in the top five feet of soil at these locations is near or below all-time lows for this time of year. Ample autumn and early-spring rains are critically needed to replenish soil moisture reserves before the commencement of the 2013 growing season.
- According to DNR Forestry, the potential for wildfires is explosively high in many areas of the state. Today's rain and snow in far northwest Minnesota has temporarily mitigated the situation there.
Contributions of information and suggestions are welcome!