Minnesota Drought Situation Report - August 2, 2007

Drought Monitor - July 31, 2007
Drought Monitor Map
Drought Monitor Legend

Drought Status
The latest U. S. Drought Monitor (see map at right) places portions of northeastern Minnesota, and most of the southern one half of Minnesota, in the Severe Drought category. With the exception of northwestern counties, the remainder of Minnesota is classified as experiencing a Moderate Drought or depicted as being Abnormally Dry. The drought situation in the northern one third of Minnesota is the result of the lingering impacts of a very dry 2006, and a snow-sparse 2006-2007 winter. The drought situation in the southern two thirds of Minnesota is due to a dry 2007 growing season (see: 12-week U.S. Drought Monitor animation). The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.

Last week's weather:
Weekly Precipitation Map Precipitation last week was generally light across the most drought stricken areas of Minnesota (see map below). Most of these locations received less than a quarter inch of rain for the seven-day period ending Monday morning, July 30. Significant rainfall was reported in just a few areas. Rainfall exceeding one inch fell in a relatively small portion of south central and southeastern Minnesota. One-inch rainfall also fell along a narrow band from Park Rapids to Duluth. Weekly temperatures were well above the long-term mean last week, enhancing evaporation rates. Maximum temperatures topped 90 degrees at least once last week in nearly every Minnesota community. Historically, the last two weeks of July and the first week of August are the warmest of the summer.

Seasonal weather overview:
Dryness has been entrenched across the southern two thirds of Minnesota for much of May, June, and July. Rainfall for the eight-week period from June 5 through July 30 totaled less than three inches over much of the southern two thirds of Minnesota (see map below). In most of these areas, rainfall totals for the period were four or more inches short of the historical average (see map below). When compared with historical rainfall totals for the same eight-week time frame, 2007 values rank at or below the 5th percentile for many central and southern Minnesota counties (see map below). In a few areas, the June 5 - July 30 rainfall totals are near all-time record low values. The timing of the dry weather is unfortunate. The period from May through September is historically the wettest time of the year in Minnesota. Long-term average rainfall rates during this time interval are around one inch per week. Very dry weather, occurring during a time of year when ample rain is typical, leads to the rapid intensification of drought. The lack of precipitation, along with very high evaporation rates, has led to deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.

June 5 to July 30 2007 Precipitation June 5 to July 30 2007 Precipitation Departure Map June 5 to July 30 2007 Precipitation Ranking Map

Growing Season (April 1 to present) precipitation totals, departure, and ranking:
Rainfall totals since April 1 are less than nine inches across much of the southern one half of Minnesota (see map below). Growing season rainfall totals have deviated negatively from historical averages by more than four inches across many central, east central, southwestern, and south central Minnesota counties (see map below). This is roughly the equivalent of missing all of June's rainfall. Seasonal rainfall deficits exceeding six inches are reported in a band that extends from Litchfield in central Minnesota eastward into portions of the Twin Cities metropolitan area. Six-inch shortfalls are also in place in some southwestern and south central Minnesota counties. When compared with other seasonal rainfall totals-to-date in the historical database, this year's rainfall for the season ranks below the 20th percentile (one year in five occurrence) in most southern Minnesota counties (see map below).

April 1 to July 30 2007 Precipitation Map April 1 to July 30 2007 Precipitation Departure Map April 1 to July 30 2007 Precipitation Ranking Map

Sector briefs:

More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.

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URL: http://climate.umn.edu/doc/journal/drought_situation_report_2007_070802.htm
Last modified: August 2, 2007