Use these links to access more detailed analyses of Global and U.S. data.
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The graph to the left shows monthly mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The 2001 value is estimated from preliminary Climate Division data using the first difference approach. September 2001 ranked as the twenty-ninth warmest September in the 1895 to present record. The preliminary nationally averaged temperature was 66.3� F (19.1� C) which was 0.9� F (0.5� C) above the long-term mean. The September temperature values from 1895 through 2001 are available. |
Just three years ago in 1998, the warmest September in the record occurred when the nationally averaged temperature reached 69.5� F (20.8� C). |
Data collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville indicate that temperatures in the lower half of the atmosphere (lowest 8 km) were below average over the U.S. for September 2001. The average lower tropospheric temperature over the continental U.S. was 0.7� F (0.4� C) below the 1979-1998 mean. This marks a change from the previous four years where temperatures were near to much above the mean. | ![]() larger image |
In general, most of the western half of the nation was warmer than average. The largest positive anomalies occurred from Montana southward into Idaho, Nevada and Arizona. Positive anomalies also occurred in many northeastern states. The bulk of the eastern half of the country and coastal areas of California and Washington experienced cooler than normal temperatures. Puerto Rico and Hawaii were near normal while Alaska was near to above normal. |
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Maps showing how the temperature anomalies varied day-to-day and how the day-to-day temperature variability compares to the long-term average are available. For further regional analysis, view NCDC's regional page.
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Positive standardized temperature anomalies for September 2001 were generally located in the western half of the nation and in portions of the northeast. Negative anomalies were present in most of the eastern half of the country with the largest anomalies occurring in south Texas, the extreme southeast and areas of the mid-Atlantic. The adjacent animated map shows the geographical pattern of temperature anomalies for the last 12 months compared to a base period of 1931-1990.
For further regional analysis, view NCDC's regional page. |
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The graph to the left is a time series depicting precipitation averaged across the nation. Based upon preliminary precipitation data, September 2001 was near average, ranking forty-sixth in the 1895 to present record. While nationally averaged precipitation was near the long term mean, there was regional variability. Nebraska and Kansas were notably wet receiving much above normal precipitation for the month. For further regional analysis, view NCDC's regional page. |
The map to the right, based on approximately 250 airport stations, shows September 2001 total precipitation as a percent of the 1961-1990 station normals. Above normal precipitation generally occurred in the Gulf coast states, around the western Great Lakes, in the central Plains and in the Midwest. The rest of the country was mostly dry including Alaska, Hawaii and Puerto Rico. For further regional analysis, view NCDC's regional page. |
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The graph to the left shows April-September mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The value is estimated from preliminary Climate Division data using the first difference approach. April-September 2001 ranked as the fourth warmest such period in the 1895 to present record. The preliminary nationally averaged temperature was 67.4� F (19.7� C) which was 1.6� F (0.9� C) above the long-term mean. The Warm Season temperature values from 1895 through 2001 are available. |
This is the fourth consecutive year where April-September temperatures have averaged above the long term mean.
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The graph to the left is a time series depicting precipitation averaged across the nation. Based upon preliminary precipitation data, April-September 2001 was near average, ranking thirty-seventh driest in the 1895 to present record. Twelve of the last thirteen April-September periods were near to above normal. For further regional analysis, view NCDC's regional page. |
The following NCDC datasets are used for the historical U.S. data: the climate division drought database (TD-9640), and the hurricane datasets (TD-9636 and TD-9697). It should be noted that the climate division drought database consists of monthly data for 344 climate divisions in the contiguous United States. These divisional values are calculated from the 6000+ station Cooperative Observer network.
For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:
Climate Services Division
For further information on the historical climate perspective presented in this report, contact:
Dimitri Chappas
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Dimitri.H.Chappas@noaa.gov
-or-
Jay Lawrimore
NOAA/National Climatic Data Center
151 Patton Avenue
Asheville, NC 28801-5001
fax: 828-271-4328
email: Jay.Lawrimore@noaa.gov