A monthly electronic newsletter summarizing Minnesota's climate conditions and the resulting impact on water resources. Distributed on the Wednesday following the first Monday of each month.
State Climatology Office - DNR Division of Ecological and Water Resources, St. Paul
prepared: August 3, 2011
What happened in July 2011:
- July 2011 precipitation totals were highly variable. Some areas, especially in central Minnesota, reported eight to ten inches of rain for the month. In those areas, July precipitation totals more than doubled the historical normal. By contrast, July rainfall totals in northeast Minnesota were less than three inches, falling short of normal by one to two inches. There were multiple days in July with torrential downpours. Two to four-inch rainfall daily totals were common and led to urban and stream flooding, road washouts, and the ponding of water.
- Monthly mean temperatures for July 2011 were well above average across Minnesota, breaking a string of seven consecutive months of below-average temperatures. July temperatures generally exceeded the historical mean by three to six degrees. Preliminary data indicate that July 2011 will rank among the ten warmest Julys in Minnesota's modern record. Extreme temperature values for July ranged from a high of 100 degrees F at Gaylord (Sibley County) on the 1st, to a low of 35 degrees F at Brimson (St. Louis County) on the 13th. The month of July was notable for the intensity, geographic extent, and duration of high dew point temperatures. Multiple days of very high dew point temperatures were reported at many locations. Dew point temperatures in excess of 75 degrees were common, and dew point temperatures exceeding 80 degrees (a rare occurrence) were reported at many locations in mid-July.
Where we stand now:
- Growing season precipitation totals to date (April through July) are above average in most Minnesota counties. In many locations, seasonal rainfall totals exceed the historical average by five or more inches. When compared with April through July rainfall totals of the past, 2011 ranks above the 90th percentile in many southwestern, central, and northwestern Minnesota communities. By contrast, some northeastern Minnesota locales rank below the 30th percentile for the period.
- The U.S. Geological Survey reports that stream discharge values remain very high in nearly every major Minnesota watershed. The National Weather Service indicates that river levels remain near or above flood stage at some locations along the Red River, and a few locales along the Mississippi and Minnesota rivers. Conversely, stream flows in northern Lake County and along the Rainy River in Koochiching County are below the 15th percentile when compared with historical data for the date.
- The U. S. Drought Monitor, released on July 28 depicts Houston County as Abnormally Dry. No other drought areas were identified in Minnesota at the end of July. The Drought Monitor authors are contemplating an Abnormally Dry designation in their next release for northern St. Louis and Lake counties. Stream flow in those areas are low due to the lingering impact of precipitation deficits during the 2010 growing season and spotty rainfall thus far this spring and summer. 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 Lake Superior water level is three inches above last year's elevation at this time, but down nine inches from the long-term seasonal average. The water level on White Bear Lake (Ramsey/Washington county border) remains quite low. However, the lake elevation is up by over one and one-half feet after reaching an all-time record low level mark in November 2010. Elsewhere across Minnesota, many lake levels are quite high relative to historical mid-summer values.
- As of July 31, the Minnesota Agricultural Statistics Service reported that topsoil moisture was 0% Very Short, 2% Short, 76% Adequate, and 22% Surplus. Hot, humid conditions and ample rainfall continue to advance crop development and help to mitigate the impact of spring planting delays.
- The potential for wildfires is currently rated by DNR Forestry as "Moderate" in far northeastern and north central Minnesota. All other Minnesota counties are considered to have "Low" wildfire potential.
- The August precipitation outlook shows a bias towards above-normal conditions over the entire state with the exception of northeastern Minnesota. The rainfall outlook for northeastern Minnesota demonstrates no significant tendencies away from historical climatological probabilities. August precipitation normals range from under three inches in northwestern and west central Minnesota to over four and one half inches in southeastern counties.
- The August temperature outlook offers equal chances of above-normal, near-normal, and below-normal conditions. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70s by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50s by late August.
- The 90-day precipitation outlook for August through October tilts towards above-normal conditions for the western one-half of Minnesota, and no significant tendencies away from historical climatological probabilities in eastern Minnesota. The August through October temperature projection leans towards above-normal conditions in southeastern Minnesota. Elsewhere across Minnesota the three-month temperature projection offers equal chances of above-normal, near-normal, and below-normal conditions.
- 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 are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS).
From the author:
- On July 1, the National Climatic Data Center released new climate normal statistics that summarize data gathered over the period from 1981 through 2010. By international agreement, these statistics are recalculated once each decade. The new normals will be the benchmark measures of central tendency for this decade. In the coming months, the new statistics will be introduced into tables and maps where "departure from normal" measures are offered.