National Overview - September 2007


NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

Maps and Graphics:


September Most Recent 3 Months Most Recent 6 Months
Most Recent 12 Months Year-to-Date US Percent Area Very Wet/Dry/Warm/Cold
Annual Summary for 2006

PLEASE NOTE: All temperature and precipitation ranks and values are based on preliminary data.  The ranks will change when the final data are processed, but will not be replaced on these pages.  As final data become available, the most up-to-date statistics and graphics will be available on the Climate Monitoring Products page and the U.S. Climate At A Glance Web site.


For graphics covering periods other than those mentioned above or for tables of national, regional, and statewide data from 1895—present, for September, last 3 months or other periods, please go to the Climate At A Glance page.

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National Overview:


Temperature Highlights
  • For the contiguous United States, the average temperature for September was 67.5°F (19.7°C), which was 2.1°F (1.2°C) above the 20th century mean and the eighth warmest September on record, based on preliminary data.
  • Unlike August, no states set record average temperatures during September. Most of the Lower 48 states had monthly averaged temperatures above normal, and no states were below the normal average temperature for the month.
  • Louisville, KY set a record high average temperature of 76.3°F (24.6°C) during September and both Key West, FL and Washington, D.C. had the third warmest average temperature for the month on record. Raleigh-Durham International Airport (NC) reported a high of 101°F (38°C) on September 10, the latest date in a calendar year with the maximum greater than 100 degrees since records began in 1944.
  • At least 60 new high temperature records were set in the Northeast region in September, the most notable in Caribou, ME on September 25th. The new record of 83°F (28°C) was 10°F (5.6°C) warmer than the previous record set in 2004.
  • Record high maximum and minimum temperature records were set in Missouri, Illinois, Indiana, Wisconsin, Michigan and Kentucky during the first five days of September. Brookville, Indiana reached an unseasonably-warm 98°F (37°C) on September 5. In contrast, record lows were set in the East North Central and northern Central regions on September 15 after the passage of a strong cold front.
  • Nome, AK was completely frost free for the months of June, July, August and September. On October 1st, the temperature dipped to 32°F (0°C), ending the 2nd longest frost-free season in Nome's 100+ years of climate record keeping. The longest frost-free season occurred back in 1989.
Precipitation Highlights
  • Although no new low precipitation records were set, this was the 22nd driest September in the 1895—2007 record. An average of 2.1 inches (53 mm) fell across the contiguous U.S. this month, which is 0.4 inches (10 mm) below average.
  • The widespread warmth and below-average rainfall in September led to an expansion of drought in the Southeast and parts of the mid-Atlantic and Ohio Valley. At the end of September, drought affected approximately 62% of the Southeast and 43% of the contiguous U.S., according to the federal U.S. Drought Monitor. In addition, 28% of the contiguous U.S. was in moderate to extreme drought. For more information on drought during September, please visit the U.S. Drought Watch page.
  • 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 trend across the Great Lakes. Preliminary data show Superior's average water level dipped 1.6 inches (41 mm) beneath the previous low for the month reached in 1926, according to NOAA's Great Lakes Environmental Research Laboratory.
  • All the Great Lakes, which together make up about 20% of the world's fresh surface water, have been in decline since the late 1990s. Lakes Huron and Michigan were about 2 feet (610 mm) below their long-term average levels, while Lake Superior was about 20 inches (510 mm) off, Lake Ontario 7 inches (180 mm) below, and Lake Erie a few inches (tens of mm) below normal in September.
  • September brought large amounts of precipitation to Minnesota, Missouri and the Upper Peninsula of Michigan, which received an estimated 10 inches (254 mm) of rainfall. These heavy rains have alleviated much of the Extreme Drought conditions in the Upper Midwest, although states in the Southern Midwest have seen little relief. Approximately 88% of the state of Kentucky was under Extreme Drought conditions by the end of the month.
  • Precipitation totals in the Northeast averaged 61% of normal, with all states reporting below-average rainfall. About half of the counties in Maryland and Pennsylvania are under a drought watch, many areas in New York reported record low reservoir levels, dried up wells and farm ponds, and water restrictions are in place in communities throughout the Northeast.
  • As of September 25, Pasadena, CA 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, CA imposed the most severe water restrictions seen in the region in years, including forcing residents to cut back on watering their lawns.
  • September 2007 was the 12th wettest on record in Anchorage, AK with 4.30 inches (109.2 mm) of precipitation, which is 1.43 inches (36.3 mm) above normal.
Other Items of Note
  • September began with numerous large fires burning across the Northern Rockies, but fire activity dissipated by the end of the month as rain and high elevation snow dampened the region. As of early October, more than 8 million acres (32,000 km²) had burned across the nation, most of it in the West.
  • Dry conditions in northern Alaska during September contributed to a very large, late-season wildfire. The Anaktuvuk River wildfire, caused by lightning, burned over 250,000 acres (1000 km²), setting a record for the largest fire on the North Slope.
  • Tornadoes occurred in conjunction with each of the three tropical systems that affected the southeastern U.S. (Gabrielle, Humberto, and Tropical Depression 10). Between September 10 and 22, each of the states in the Southeast region reported tornadic activity.
  • La Niña conditions were present in the tropical Pacific Ocean by the end of September. Sea-surface temperature (SST) anomalies have become increasingly negative in the central and eastern equatorial Pacific and remain positive in the western Pacific. Nearly all of the dynamical and statistical models are forecasting weak-to-moderate La Niña conditions strengthening and persisting during the next several months. A developing La Niña may result in wetter than normal conditions in the Pacific Northwest and drier than normal conditions in the southwestern U.S. in the fall. To be considered a full-fledged La Niña episode, a negative Oceanic Niño Index (ONI) less than or equal to -0.5°C must be exceeded for a period of at least five consecutive months. The most recent ONI value (June—August 2007) is -0.2°C. For additional information on ENSO conditions, please visit the NCDC ENSO Monitoring page and the latest NOAA ENSO Advisory.

For additional details about recent temperatures and precipitation across the U.S., see the Monthly and Seasonal Highlights section below and visit the September Climate Summary page. For information on local temperature and precipitation records during the month of September, please visit NCDC's Extremes page. For details and graphics on weather events across the U.S. and the globe please visit NCDC's Global Hazards page.

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Monthly and Seasonal Highlights:


Contiguous U.S.:

For additional national, regional, and statewide data and graphics from 1895-present, for September, the last 3 months or other periods, please visit the Climate At A Glance page.
  • September Temperature: 8th warmest September in the 1895—2007 record.  The preliminary nationally-averaged temperature was 67.54°F (19.74°C), which was 2.10°F (1.17°C) above the 1901—2000 (20th century) mean.

  • September Precipitation: 22nd driest nationally in the 1895—2007 record. An average of 2.09 inches (53.1 mm) fell over the contiguous U.S. in September, which was 0.39 inches (9.9 mm) below the 20th century mean for the month.

  • July—September Temperature (3-Month): 3rd warmest in the 1895-to-present record, 1.98°F (1.10°C) above the 20th century mean. The preliminary nationally-averaged July—September temperature was 72.82°F (22.68°C).

  • July—September Precipitation (3-month): An average total of 7.38 inches (186.9 mm) of precipitation fell during this 3-month period, which corresponds to a ranking of 28th driest over the 1895—2007 period and is 0.45 inches (11.4 mm) below the 20th century July—September mean.

  • April—September (6-month): The national average temperature was the 7th warmest for this 6-month period. The preliminary nationally-averaged temperature was 67.26°F (19.59°C), which was 1.45°F (0.80°C) above the 20th century mean. At 15.56 inches (395.2 mm), the April—September precipitation was below average and ranked as the 42nd driest such period in the 1895—2007 record with 0.47 inches (11.9 mm) below the mean.

  • January—September (Year-to-date): The 9th warmest January—September on record. The preliminary nationally-averaged year-to-date temperature was 57.35°F (14.08°C), or 1.46°F (0.81°C) above the mean. The year-to-date period was the 29th driest January—September in the 113-year record, receiving a national average of 21.67 inches (55049 mm) of precipitation during the period, or 1.00 inches (25.4 mm) below the 20th century mean.

  • October 2006—September 2007: This was the 8th warmest such period in the 1895—2007 record.  The preliminary nationally-averaged annual temperature was 54.22°F (12.34°C), which was 1.40°F (0.78°C) above the mean. Precipitation for the October 2006—September 2007 period ranked as the 53rd wettest October to September in the 112-year record.  The nationally-averaged annual precipitation accumulation was 29.37 inches (746.0 mm), ranking 0.23 inches (5.7 mm) above the 20th century mean.

Alaska:
  • Alaska had its 12th warmest September since records began in 1918, with a temperature 2.61°F (1.45°C) above the 1971—2000 average.

  • Alaska had its 2nd warmest July—September on record, with a temperature 2.38°F (1.32°C) above the 1971—2000 average.

  • Alaska had its 24th warmest January—September on record, with a temperature 0.61°F (0.34°C) above the 1971—2000 average.

  • Nome, Alaska was frost free for the entire months of June, July, August & September. October 1, the temperature dipped to 32 degrees, ending the 2nd longest frost-free season in Nome's 100+ years of climate record keeping.

  • Anchorage, Alaska was warmer and wetter than normal. September 2007 was the 12th wettest on record in Anchorage with 4.30 inches, 1.43 inches above normal. Anchorage's average high of 56.9 degrees was 1.9 degrees above normal, and the minimum average temperature of 43.9 was 2.5 degrees above normal.

Other Statewide and Regional Highlights:
  • The average September temperatures did not set any new statewide records in September. However, the monthly average temperatures were much above normal in New Jersey and Rhode Island. September was relatively warm across the nation; only ten states in the Continental U.S. had temperatures near normal, no states had temperatures below normal, and the rest were above normal. Maryland had its third driest September on record, New Jersey had its 4th driest September, Delaware had its fifth driest and Illinois had its tenth driest September since 1895. No states had precipitation amounts much above normal during September.

  • July—September temperatures across Colorado, Utah and Wyoming were the warmest on record. It was the second-warmest July—September in Florida in the past 113 years. Despite the heavy rains brought by the remnants of Hurricane Humberto, North Carolina set a new record for the least precipitation with an average of 7.6 inches (194 mm) from July—September, which is 7.9 inches (200 mm) below normal. Delaware had the second-driest July—September period and South Carolina had the 3rd driest July—September period on record. In contrast, Texas had its 11th wettest July—September period on record.

  • Temperatures over the past 6 months (April—September) were much above average in the western half of the Continental U.S. The past sixth months were the fourth warmest in the West, fifth warmest in the Southwest, and seventh warmest in the West North Central U.S. on record. A lack of precipitation in the Southeast made this the third driest April—September on record for the region and the 8th driest in the Central U.S. In contrast, this was the 10th wettest April—September on record in the South.

  • April—September (6-month) temperatures were above average for 34 states. This was the second-warmest April—September period in Nevada, Utah and Wyoming and the third-warmest in Idaho. Only two states had temperatures below normal for this period. Both Tennessee and North Carolina had the driest April to September period on record, and Kentucky had its 2nd driest. In contrast, both Oklahoma and Texas experienced the 4th wettest such period on record.

  • So far during 2007, temperatures have been above average for most of the Continental U.S. and much above average for eight states, including Arizona, Idaho, Utah and Wyoming. It was the 29th coolest January—September on record in Texas. North Carolina and Tennessee had the driest such period on record, Alabama had its 2nd driest, and Kentucky had its 3rd driest. In contrast, Texas experienced its wettest January through September on record and Oklahoma its 4th wettest.

  • Regionally, the January—September precipitation across the Southeast was the driest on record. It was the 9th driest in the West region and 8th wettest in the South region.

  • Average temperatures over the past twelve months from October 2006—September 2007 were near average to much warmer than average for nearly all of the Lower 48 States. Six states, including Idaho and Wyoming, experienced average temperatures much above normal. Only Texas experienced temperatures below normal during this period. The West North Central region had temperatures much above normal. Precipitation during this period varied sharply from one region to another. The precipitation in the West ranked as the 3rd driest October—September period and the Southeast experienced its 7th driest. Tennessee had its 2nd driest October—September on record, Florida its 4th, and California its 5th driest. In contrast, both Oklahoma and Texas were the 3rd wettest during the past twelve months. The South had its 5th wettest October—September in the 112-year record.
See NCDC's Monthly Extremes web-page for weather and climate records for the month of September.

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PLEASE NOTE: All of the temperature and precipitation ranks and values are based on preliminary data.  The ranks will change when the final data are processed, but will not be replaced on these pages.  Graphics based on final data are available on the Climate Monitoring Products page.

Citing This Report

NOAA National Climatic Data Center, State of the Climate: National Overview for September 2007, published online October 2007, retrieved on August 30, 2014 from http://www.ncdc.noaa.gov/sotc/national/2007/9.