Drought - September 2007

Contents Of This Report:
Map showing Palmer Z Index

Top of Page National Overview

  • Based on the Palmer Drought Index, severe to extreme drought affected about 28 percent of the contiguous United States as of the end of September 2007, an increase of about 1 percent compared to last month. By contrast, about 12 percent of the contiguous U.S. fell in the severely to extremely wet categories.
  • About 43 percent of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of September.
  • On a broad scale, the previous two decades (1980s and 1990s) were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness (moderate to extreme drought, severe to extreme drought).
  • A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
  • Historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page in files having names that start with "drd964x" and ending with "txt" (without the quotes).

Top of Page Detailed Drought Discussion

During September 2007, drought expanded in the mid-Atlantic States, decreased in the northern Great Lakes, and continued to affect a large part of the western U.S. (U.S. Drought Monitor for end of August vs end of September).

The month was unusually dry across much of the eastern seaboard, from Maine to the Carolinas, and across parts of Florida. The September dryness extended across the Ohio Valley and into the southern Great Lakes. A drier-than-normal month was also experienced across parts of the Pacific Northwest and northern Plains. Northern stations in Alaska were drier than normal while central and southern stations were wetter than normal. Above-normal rainfall was reported at some Hawaiian stations this month, but most of the islands were dry, continuing a dry pattern which has lasted several months. September was drier than normal across parts of southeastern Puerto Rico, continuing a trend which has lasted much of the year.
Map showing September Station Precipitation Anomalies
A subtropical high pressure system has been responsible for blocking rainfall across much of the Southeast this month and much of the spring and summer. The September dryness compounded the earlier moisture deficits to result in extremely to exceptionally dry conditions from 3-months to 6-months and beyond. In some southeast states (North Carolina and Tennessee), the dryness of recent months has been so persistent and severe that the long-term Palmer Drought Index has reached near-record severity in a short time compared to previous severe droughts.
Map showing 6-Month Standardized Precipitation Index
Map showing U.S. Drought Monitor

North Carolina and Tennessee had the driest year-to-date (January-September) and last 6 months (April-September) on record. In fact, the 2007 statewide precipitation rank for North Carolina was driest in 113 years for January-September and for the multi-month seasons April-September through August-September. For Tennessee, each multi-month season from November-September through May-September ranked as driest on record.
Graph showing North Carolina Statewide Precipitation, May-September, 1895-2007
Just under two-thirds of the western U.S. (Rockies westward) fell in the moderate to extreme drought category, and about 43% fell in the severe to extreme category (as defined by the Palmer Drought Index) by the end of this month.
Graph showing Southeast Precipitation Departures and Normals, January 1998 - September 2007
The persistent dryness has depleted soil moisture, ravaged crops, and dried up streams. Pasture and rangeland conditions were most severely stressed in the eastern and western thirds of the country. Soil moisture (both modeled and observed) and streamflow (both modeled and observed) were most severely affected in the three core drought areas: the Southeast, upper Great Lakes, and West.

A more detailed drought discussion can be found below.


For most areas of the Southeast during September, as summarized by the Southeast Regional Climate Center, the continuing drought was a major climatic concern. Three tropical storms affected the region, bringing 6 to 8 inches of rain in some areas. But these amounts were generally rather isolated, localized events -- the prolonged, widespread downpours hoped for by many did not materialize. Nevertheless, almost all areas got some precipitation -- not enough to remove the drought, but sufficient to prevent any records for "longest dry spell" being broken. As a result, drought in September was less severe than in August for northern Virginia, southern (especially southeast) Georgia, and much of Florida outside the panhandle. However, the western and central parts of the region continued to have Exceptional Drought, with some places having an increase in severity.

As noted by the Southeast Regional Climate Center, for much of the Southeast, the overall severity of the prolonged drought led to water use restrictions being considered in many municipalities and implemented in some.

Some specifics:
  • In early September, the South Carolina Drought Response Committee upgraded the drought level to severe for most of the state based on the drought impact to agriculture, forestry, and hydrology.
  • As reported by Greenwire (9/11), the Southeast drought has lowered rivers in Alabama to the point where there is insufficient streamflow to meet the demand of industry, agriculture, municipalities, and natural evaporation. Alabama Power, the state's largest utility, has been operating some of its coal plants at significantly reduced levels to avoid raising water temperatures in the Coosa, Black Warrior and Mobile rivers. Last month, the Tennessee Valley Authority shut down Brown's Ferry Number 2 nuclear power plant due to inadequate streamflow. Alabama Power spokesman Michael Sznajderman said, "Come the latter part of September, if the flows continue to be so low at a number of our hydro facilities ... basically the turbines are going to come out of the water." At least four large pulp mills on the Alabama and Black Warrior rivers had to suspend wastewater discharges for days at a time to avoid violating their discharge permits.
  • In early September, Governor Mike Easley asked local officials across North Carolina to implement water conservation measures in their cities and counties, if they hadn't already done so. The governor had earlier directed state agencies in all 100 counties to stop non-essential water use, issued a statewide ban on open burning, and asked the USDA to declare the state an agricultural federal disaster area.
  • At the end of September, the Georgia Environmental Protection Division declared a level four drought response across the northern third of the state, which prohibits most types of outdoor residential water use.


As noted by the Northeast Regional Climate Center, with 4 of the previous 5 months yielding below normal precipitation, drought conditions, while not as bad as other areas of the country, expanded in the Northeast. By month's end, the U.S. Drought Monitor had parts of western and northern New York and southwestern West Virginia under Severe Drought conditions. Adjacent to those areas as well as parts of central Connecticut, south central Massachusetts, southern New Jersey, and most of Maryland and Delaware were moderately or abnormally dry. According to the USGS, streamflow was much below normal from eastern Massachusetts to the Washington, DC metro area.

Locally, Maryland and Pennsylvania had about half of their counties under a drought watch. In New York, rainfall in the Northern Plateau climate division for August and September was 50% of normal, making the 2-month period the 2nd driest on record. Many areas in upstate New York reported record low reservoir levels and dried up wells and farm ponds. The Canal Corp. diverted water from one reservoir to give relief to another reservoir that is used to power electric plants as well as provide municipal water. Water restrictions were in place in communities throughout the Northeast. On September 14, the USDA made low-interest emergency loans available to farmers affected by drought conditions in Pennsylvania, Maryland and New York. The Small Business Administration announced that small businesses affected by the drought in West Virginia were eligible for federal disaster loans due to drought conditions.


As explained by the Midwest Regional Climate Center, precipitation was quite variable across the Midwest during September. Heavy rain that fell over the arrowhead of Minnesota, which had been suffering from Extreme Drought (D3) conditions for much of the summer, helped to nearly wipe out the excessive drought conditions. Overall, drought conditions improved throughout the northern half of the Midwest. All of the states have seen improvement, nearly eliminating the Extreme Drought conditions (as measured by the U.S. Drought Monitor). Conditions across the southern part of the region deteriorated, especially in Kentucky where over half of the state received less than 50% of the rain that typically falls during the month. Heavy rain in the third week of September brought some relief to central Kentucky. Unfortunately, dry weather again took hold and Extreme Drought conditions overtook more than 88% of the state (a 17% increase from the previous week). Drought conditions are also creeping slowly northward into central Illinois, Indiana and Ohio after a slight retreat during the third week of the month.

According to an Associated Press report, drought and mild temperatures have pushed Lake Superior's water level to its lowest point on record for this time of year, continuing a downward spiral across the Great Lakes. Preliminary data showed that Superior's average water level in September dipped 1.6 inches beneath the previous low for that month reached in 1926, according to NOAA's Great Lakes Environmental Research Laboratory. The U.S. Army Corps of Engineers, which uses a different measuring technique, calculated the September level at 4 inches below the record. Either way, the lake has plummeted over the past year and has dipped beneath its long-term average level for a decade -- the longest such period in its known history. Some areas had so little water last spring and summer that recreational boats couldn't reach docking slips. Commercial shippers, who haul iron ore and coal across the lakes to manufacturing centers such as Detroit, have been unable to fill cargo holds to capacity for fear of scraping bottom in shallow channels. All the Great Lakes, which together make up about 20 percent of the world's fresh surface water, have been in decline since the late 1990s. Lakes Huron and Michigan were about 2 feet below their long-term average levels, while Lake Superior was about 20 inches off, Lake Ontario 7 inches below, and Lake Erie a few inches down.


This year has been very dry in southern California. As of September 25, Pasadena experienced its driest year since records began in 1878, and the mayor has asked Pasadena residents to voluntarily conserve water. In early September, Long Beach imposed the most severe water restrictions seen in the region in years, including forcing residents to cut back on watering their lawns and requiring restaurants to only serve water when customers request it. Mandatory water restrictions were also in place in Sierra Madre.

According to media reports, drought conditions have forced the closure of one electricity-generating unit at Palisades Reservoir and are affecting the quality of water coming out of American Falls. Both of these Idaho reservoirs were all but empty by September. Water from Jackson Lake reservoir in northwest Wyoming was being tapped to provide irrigation water to farmers across the Snake River Valley in southern Idaho.

During September, the USDA designated several counties in various states as drought disaster areas. These include counties in Minnesota, Pennsylvania, North Carolina, Delaware, and Virginia.

Top of Page State/Regional/National Moisture Status

A detailed review of drought and moisture conditions is available for all contiguous U.S. states, the nine standard regions, and the nation (contiguous U.S.):

Alabama Arizona Arkansas California Colorado Connecticut
Delaware Florida Georgia Idaho Illinois Indiana
Iowa Kansas Kentucky Louisiana Maine Maryland
Massachusetts Michigan Minnesota Mississippi Missouri Montana
Nebraska Nevada New Hampshire New Jersey New Mexico New York
North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania
Rhode Island South Carolina South Dakota Tennessee Texas Utah
Vermont Virginia Washington West Virginia Wisconsin Wyoming

Northeast Region East North Central Region Central Region
Southeast Region West North Central Region South Region
Southwest Region Northwest Region West Region
Map showing the nine U.S. standard regions
Contiguous U.S.

Top of Page Pre-Instrumental Perspective

There is no September 2007 Paleoclimatic Perspective.

Citing This Report

NOAA National Centers for Environmental Information, State of the Climate: Drought for September 2007, published online October 2007, retrieved on July 2, 2020 from https://www.ncdc.noaa.gov/sotc/drought/200709.