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Climate of 2002 - August National Temperatures National Climatic Data Center, 13 September 2002

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Contents: Summer Temperatures August Temperatures Temperature Departures 12-month Temperatures U.S. Precipitation

Click on links throughout the text of this report for more maps and graphs.

National Summer Season Temperatures - June-August 2002

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The graph to the left shows seasonal mean temperature averaged across the contiguous United States based on long-term data from the U.S. Historical Climatology Network (USHCN). The value for June-August 2002 (climatological summer) is estimated from preliminary Climate Division data using the first difference approach. June-August 2002 ranked as the 3rd warmest such period in the 1895 to present record after the summers of 1936 and 1934. The preliminary nationally averaged temperature for summer 2002 was 73.9° F (23.3° C) which was 1.8° F (1.0° C) above the long-term mean.

Statewide mean temperature for the June-August period was much above average for 17 states, with New Jersey and Nevada having their 2nd warmest summer 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 summer months. Over the June-August period, no state-averaged temperature was significantly cooler than the long-term mean. When broken down by climate division however, there are some cooler than average divisions in Montana, Maine, Texas, Mississippi and Florida, and one division in Oklahoma, as can be seen in the map to the right. Record warm temperatures averaged over the June-August period were recorded in several divisions (in New Jersey, Colorado and Nevada and a small section of eastern California). Temperatures in Alaska were above average for the summer season. In the last 15 years, there have only been 4 summers in Alaska with below average temperatures. The pattern of summer 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 June-August period, they were associated with warmer than average temperatures across the mid-section of the contiguous U.S. from the Southwest and West across to the Northeast. Averaged over the summer months, there were no significant negative height anomalies and where the height anomalies were near average (the southern tier of the U.S. and Montana), so were the Statewide temperature averages.

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August 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. August 2002 ranked as the 24th warmest August in the 1895 to present record. The preliminary nationally averaged temperature was 73.7° F (23.2° C) which was 0.9° F (0.5° C) above the long-term mean. The August temperature values from 1895 through 2002 are available.

Much above average warmth occurred in 9 northeastern states in August. No statewide mean temperature records were set in August, though many states stretching from the Southwest to the Northeast (seen in the map below) were warmer or much warmer than average for the month.

New Jersey had its third warmest August on record and Rhode Island, its 4th. Cooler than average temperatures were evident in the parts of Northwest, northern Rockies and northern High Plains, and also in a few areas of the Southeast as can be seen in the map of divisional temperature (below right). Temperatures in Alaska were slightly below normal at -0.36°F (-0.2°C) relative to the period 1971-2000. The pattern of warmth and cold in the contiguous U.S. in August broadly corresponds with the mean 500mb height and anomalies chart. This shows that above normal 500mb heights existed across the Northeast and Great Lakes with the largest anomalies occurring over the Great Lakes region. The warmest monthly mean statewide temperatures were displaced slightly to the east and south of the largest positive height anomalies. Much of the warmth in the Northeast occurred during the 2nd full week of the month when daily average temperature anomalies in excess of 12°C (21.6°F) were recorded. The warmth was alleviated late on the 19th and replaced by the same cool air mass which had persisted in the northern Great Plains leading to the cooler than average monthly temperatures in that region.

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Regional Temperature Ranks for the
Contiguous U.S., August 2002

Region	Rank
Northeast	99th coldest
East North Central	61st coldest
Central	90th coldest
Southeast	75th coldest
West North Central	43rd coldest
South	70th coldest
Southwest	90th coldest
Northwest	39th coldest
West	66th coldest

Temperature Departures

The map to the right, based on over 500 airport stations, shows departures from the 1971-2000 normal temperatures for August 2002. Warmer than average temperatures extended from the Southwest to the Northeast, with the largest positive departures in the contiguous U.S. (greater than 6.0° F [3.3° C]) occurring in the Northeast. The largest negative temperature anomalies were recorded in the northern Great Plains, northern Rockies and Northwest with some cooler than average temperatures also occurring along the southern coast of California and the Southeast. An animated map of daily temperature anomalies shows temperature variability throughout the month of August.

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National Temperatures - September 2001-August 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). The value for the last 12 months is estimated from preliminary Climate Division data using the first difference approach. September 2001-August 2002 ranked as the 4th warmest such period in the 1895 to present record. The preliminary nationally averaged temperature was 54.4°F (12.4°C) which was 1.6°F (0.9°C) above the long-term mean.

Record warmth occurred in three states (RI, NJ and DE) averaged over the last twelve months. The pattern of state-averaged monthly temperature can be seen in the map to the right. Twenty-six other states ranked in the top ten warmest such periods. Only five states had near-average temperatures for September-August (LA, MS, AL, AR and MT).

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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:

Climate Services Division NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4876 phone: 828-271-4800 email: questions@ncdc.noaa.gov

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

NCDC / Climate Monitoring / Climate of 2002 / August / U.S. Temp. / Search / Help