Major Highlights
U.S. HAS MILDER SEPTEMBER AFTER NEAR RECORD WARM SUMMER
GLOBAL SEPTEMBER TEMPERATURE 4TH WARMEST ON RECORD
September 2006 was cooler than average for the continental U.S., providing relief from the seemingly unrelenting heat of summer. The unusually warm temperatures affecting the nation during much of 2006 were replaced by below average temperatures in many places, and this was the first cooler than average month for the continental U.S. since May, 2005, according to scientists at NOAA's National Climatic Data Center in Asheville, N.C. Drought conditions also improved in some areas of the nation with nationally averaged precipitation above average during September.
U.S. Temperature Highlights
The September 2006 temperature for the contiguous United States (based on preliminary data) was 0.7°F (0.4°C) below the 20th century average of 65.4°F (18.6°C). This was the first cooler-than-average month since May 2005, based on the century-scale average. The rarer nature of below-average national temperatures is reflective of the overall long-term warming trend for the nation.
With six of the first nine months of the year much warmer than average, the year-to-date (January-September) temperature remained record warmest again this month. The previous record warm January-September occurred in the year 2000.
The September temperature was below average in 25 states of the continental U.S. while above-average temperatures occurred in only five (Vermont, Montana, Idaho, Washington, and Oregon).
September temperatures for the state of Alaska were warmer than average, 2.7°F (1.5°C) above the 1971-2000 mean of 45.9°F (7.7°C), the 11th warmest September since statewide records began in 1918.
U.S. Precipitation Highlights
Wetter than average conditions in September occurred from the northern High Plains to the Southwest and from New York to the mid-Mississippi Valley, and for the nation as a whole precipitation was above average.
It was a record-tying September for Kentucky, where 8.02 inches of rain fell during the month, tying 1979 for the wettest September on record for the state.
A wetter than average summer monsoon season for much of the Southwest ended in September. Following the second driest winter on record in the Southwest region, precipitation during the past few months ended drought in New Mexico and helped reduce drought severity in other parts of the region. However, below average reservoirs and other longer term hydrological effects remain widespread.
The percent of the nation affected by drought fell for the second month in a row. According to the U.S. Drought Monitor, 33% of the continental U.S. was in moderate to exceptional drought at the end of September, a decrease of 11% since the end of August.
Severe to exceptional drought remained across large parts of Arizona, southern Oklahoma to south Texas, areas of the northern high Plains and the northern Rockies, as well as northern Minnesota.
Drier than average conditions in September across the Far West contributed to the continuation of a very active wildfire season for the nation. By early October, more than 9 million acres had burned since the beginning of the year, the vast majority in the continental U.S., according to the National Interagency Fire Center. This exceeded the previous record for an entire year, set in 2005 when 8.7 million acres burned, much of it in Alaska.
Global Highlights
It was the 4th warmest September since records began in 1880 for global land- and ocean-surface temperatures (1.01°F/0.56°C above the 20th century mean). An El Niño episode began in September as ocean temperatures in the central and eastern equatorial Pacific continued a recent warming trend. Global ocean temperatures for the month were the 3rd warmest on record.
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