National Overview - September 2002


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Top of Page September Temperatures

National Temperature Time Series
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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 value for 2002 is estimated from preliminary Climate Division data using the first difference approach. September 2002 ranked as the 7th warmest September in the 1895 to present record. The preliminary nationally averaged temperature was 67.7° F (19.8° C) which was 2.2° F (1.2° C) above the long-term mean. The September temperature values from 1895 through 2002 are available.
Much above average warmth occurred in 11 contiguous states in September. No statewide mean temperature records were set for the month, though New Hampshire and Vermont had their second warmest September since 1895 and their warmest September in over 40 years. No state averaged temperature was significantly cooler than the mean for the month with only 4 (WA, UT, CO, TX) out of the lower 48 states having near average temperatures.

Significantly cooler than average temperatures were evident only in southeastern Texas as can be seen in the map of divisional temperature (below right). The pattern of warmth and cold in the contiguous U.S. in September broadly corresponds with the mean 500mb height and anomalies chart. This shows that well above normal 500mb heights existed across the northeastern quadrant of the country, which is associated with the much higher than average temperatures in September. Temperatures in Alaska were above normal relative to the period 1971-2000 for the second consecutive September.
mean 500mb height and anomalies
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State Temperature Ranks
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Regional Temperature Ranks for the
Contiguous U.S., September 2002
Region Rank
Northeast 104th coldest
East North Central 98th coldest
Central 95th coldest
Southeast 90th coldest
West North Central 87th coldest
South 82nd coldest
Southwest 70th coldest
Northwest 73rd coldest
West 88th coldest

Top of Page Temperature Departures

The map to the right, based on over 500 airport stations, shows departures from the 1971-2000 normal temperatures for September 2002. Warmer than average temperatures extended across the entire eastern half of the contiguous U.S., with some of the largest departures (greater than 6°F [3.3°C]) occurring in the Northeast and central and eastern Great Lakes region. Negative temperature anomalies were limited to coastal southern California and scattered stations from southeastern Texas to Seattle, Washington. An animated map of daily temperature anomalies shows temperature variability throughout the month of September. National Temperature Departures
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Top of Page July-September 2002

National Temperature Time Series
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The graph to the left shows mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The value for July-September 2002 is estimated from preliminary Climate Division data using the first difference approach. July-September 2002 ranked as the 4th warmest such period in the 1895 to present record. The last 6 July-Septembers have been above average. The year 1998 was the warmest July-September on record followed by 1936 and 1931. The preliminary nationally averaged temperature for July-September 2002 was 72.6° F (22.6° C) which was 1.7° F (0.9° C) above the long-term mean.



Statewide mean temperatures for the July-September period were warmest on record for five states (New Hampshire, Rhode Island, New Jersey, Massachusetts, and Nevada) and much above average for a further 14 states, with Connecticut and Vermont having their second warmest July-September on record.

Significantly above average statewide mean temperatures also occurred in all but 2 (TX and MS) of the remaining contiguous states with no state during July-September period, averaging temperatures significantly cooler than the long-term mean. Even when broken down by climate division (see graph below right), there are only 4 divisions which were significantly cooler than average during this period and these occurred in central Texas. Record warm temperatures averaged over the July-September period were recorded in several eastern divisions (Ohio, New York, Vermont, New Hampshire, Massachusetts, Rhode Island and New Jersey) and two western divisions (Nevada and California).

Temperatures in Alaska were above average for the three months. In the last 10 years, there have only been 3 July-Septembers in Alaska with below average temperatures.

State Temperature Ranks
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500mb height and anomalies
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Visual Text Separator

Top of Page January-September 2002 (year-to-date)

National Temperature Time Series
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The graph to the left shows mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The value for January-September 2002 is estimated from preliminary Climate Division data using the first difference approach. January-September 2002 ranked as the 7th warmest such period in the 1895 to present record with 4 of those 7 years occuring since 1990. The year 2000 was the warmest January-September on record followed by 1934, 1998, 1990, 1921, and 1986. The preliminary nationally averaged temperature for January-September 2002 was 57.3° F (14.1° C) which was 1.4° F (0.8° C) above the long-term mean.

Statewide mean temperature for the January-September period was much above average for 19 states, with Delaware having its record warmest January-September in 108 years. New Hampshire, Rhode Island, Connecticut, New Jersey and Maryland all had their second warmest January-Septembers on record.


Significantly above average statewide mean temperatures also occurred in 39 out of the 48 contiguous states with the remainder showing near average temperatures for the year-to-date. Over the January-September period, no state-averaged temperature was significantly cooler than the long-term mean. Even when broken down by climate division, there are only 4 divisions which were significantly cooler than average during this period and these occurred in Montana, Idaho and Arkansas, as can be seen in the map below right. Record warm temperatures averaged over the January-September period occurred in several east coast divisions (in Virginia, Maryland, Delaware, New York, Connecticut and Massachusetts).

The pattern of January-September temperature for the contiguous U.S. corresponds quite well with height anomalies in the 500mb level of the atmosphere. Though the positive height anomalies were not large for the January-September period, they were associated with warmer than average temperatures across the East and mid-section of the contiguous U.S., as well as the Southwest. Averaged over the last 9 months, there were no significant negative height anomalies and where the height anomalies were near average (the Northwest Central region), so were the Statewide temperature averages.
State Temperature Ranks
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500mb height and anomalies
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Visual Text Separator

Top of Page National Temperatures - October 2001-September 2002

National Temperature Time Series
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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). October 2001-September 2002 ranked as the 3rd warmest such period in the 1895 to present record. The preliminary nationally averaged temperature was 54.6°F (12.6°C) which was 1.8°F (1.0°C) above the long-term mean.
Record warmth occurred in eight states (NY, NH, MA, RI, CT, NJ, DE and MD) averaged over the last twelve months. The pattern of state-averaged monthly temperature can be seen in the map to the right. Twenty-four other states ranked in the top ten warmest such periods. Only three states had near-average temperatures for October-September (MS, MT and ID). State Temperature Ranks
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Top of Page September Precipitation

National Precipitation Time Series
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The graph to the left is a time series depicting precipitation averaged across the contiguous U.S. Based upon preliminary precipitation data, September 2002 was slightly wetter than average, ranking 74th driest (35th wettest). There has been no significant trend in mean national September precipitation over the last century, though September is one of only 3 months in 2002 which has averaged slightly more precipitation than the mean.
There was considerable regional variability in precipitation across the country. Four states in the South (Mississippi, Alabama, Tennessee and Kentucky) and one in the Southwest (New Mexico) received much above average rainfall in September, while one state (California) received much below average rainfall this month. Mississippi and Tennessee were second wettest on record for the month of September. November 2001 was the last month that Colorado received above average precipitation before this month. However, despite the wetter than average September, it will still take many months of above average or near average rainfall to alleviate the long-term drought in that state and others in the Southwest and West. Much of the above-average rainfall in the eastern half of the country was a result of Tropical Storm Isidore as it moved inland off the Gulf of Mexico on the 26th. More details on September hurricanes and tropical storms can be found here. State Precipitation Ranks
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satellite image
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In Indiana on September 20th, storms occurred ahead of a strong cold front leading to numerous reports of tornadoes and significant rainfall. At least two F2 tornadoes and one F3 tornado caused significant damage in Indiana. The path of the F3 tornado was 112 miles in length, though the tornado was not at that intensity for most of the distance. Twenty-seven separate reports of tornadoes were submitted to the Storm Prediction Center - 24 in Indiana and 3 in Ohio. Although it is not unusual for tornadoes to occur in the Midwest at this time of year, the intensity of this outbreak was fairly unusual. Where the F3 tornado passed through Marion County, damage estimates have reached $36M for that county alone. (Information courtesy of the Midwest Regional Climate Center's Climate Watch).


Earlier in the month, on Monday September 2nd, a tornado ripped through the town of Ladysmith, in northwestern Wisconsin. A few dozen injuries were reported and significant structural damage occurred in the town of 4,000 residents.

Further details on flooding and rainfall in the Southeast and parts of the Gulf Coast are given on the Atlantic hurricane page, as they relate to landfalling tropical storms in September.

Regional Precipitation Ranks for the
Contiguous U.S., September 2002
Region Rank
Northeast 81st driest
East North Central 36th driest
Central 75th driest
Southeast 82nd driest
West North Central 36th driest
South 74th driest
Southwest 101st driest
Northwest 23rd driest
West 26th driest

Top of Page Precipitation Departures

The map to the right, based on more than 500 airport stations, shows September 2002 total precipitation as a percent of the 1971-2000 station normals. Above normal precipitation generally occurred in the South through the Mississippi Valley and Tennessee/Ohio Valley regions, with more than 190% of normal precipitation falling in some areas. Parts of the Southwest also received more rainfall that normal, however, dryness extended across most of the West and Northwest where as little as 25% of normal rainfall was recorded. The Central Plains were also dry this month, with less rainfall than normal also extending into Michigan. National Precipitation Departures
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Top of Page Last 3 months (July-September)

National Precipitation Time Series
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The graph to the left is a time series depicting precipitation averaged across the contiguous U.S. Based upon preliminary precipitation data, July-September 2002 was wetter than average, ranking 73rd driest (36th wettest) in the last 108 years. This belies considerable regional variability as can be seen from the maps below.
State Precipitation Ranks
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State Precipitation Ranks
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Record dryness averaged over July-September occurred in California in 2002. Three other states in the West (OR, NV, and WA) and one in the East (NH) also received much below average precipitation while fifteen other contiguous states received significantly below average precipitation. All Gulf Coast states as well as New Mexico, Tennessee and part of the Upper Midwest and Northern Plains received above average rainfall for the July-September period, with Minnesota at a rank of 4th wettest for the 3 months, and record wetness for Mississippi. Though July was quite wet for Mississippi, much of the 3-month average rainfall came in September from Tropical Storm Isidore and is discussed below and on the Atlantic hurricane season web-page. Minnesota has received much above average rainfall in three of the last four months.
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Top of Page National Precipitation - October 2001-September 2002

National Precipitation Time Series
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The graph to the left is a time series depicting precipitation averaged across the contiguous U.S. Based upon preliminary precipitation data, October 2001-September 2002 was drier than average, ranking 29th driest in the last 107 such periods. The last 3 October-September periods have averaged below the long term mean precipitation.
Record dryness occurred in 2 states (CO and AZ) averaged over the last 12 months. The pattern of state-averaged October-September precipitation can be seen in the map to the right. Twelve other states ranked in the top ten driest such periods. More information on drought analysis for these states and others can be found on NCDC's Drought Pages. Four states (MN, WI, IN and MI) received much above average rainfall for the 12-month period, with a second wettest October-September occurring in Indiana. State Precipitation Ranks
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Citing This Report

NOAA National Climatic Data Center, State of the Climate: National Overview for September 2002, published online October 2002, retrieved on December 22, 2014 from http://www.ncdc.noaa.gov/sotc/national/2002/9.