National Climatic Data Center, 11 October 2002

September Temperatures

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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.

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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

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.

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July-September 2002

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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.

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January-September 2002 (year-to-date)

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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.

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National Temperatures - October 2001-September 2002

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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).

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Questions?

For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:

For further information on the historical climate perspective presented in this report, contact:

Catherine Godfrey NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4328 email: Catherine.S.Godfrey@noaa.gov

Jay Lawrimore NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4328 email: Jay.Lawrimore@noaa.gov

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