Wildfires - May 2009

Update: 08 June 2009

While the nation saw above average fire activity in May 2009, the month was relatively quiet when compared to that of preceding months. May began with 12 active large fires, primarily in Florida and the eastern parts of Kentucky and Tennessee. By mid–month, 12 fires were present in five states, of which five occurred in Florida and three in Texas. Torrential rains toward the end of May assisted in extinguishing the active large fires in Florida, and by the end of the month, only five large fires were burning, one each in Florida, Arizona, California, Oregon, and Alaska.

Large Fire Maps:

According to statistics from the National Interagency Fire Center (NIFC), between May 1st and May 29th approximately 312,599 acres (126,504 hectares) were burned across the United States. The total acreage burned during May 2009 was 115,436 acres (46,715 hectares) above the 2000–2009 average of 197,163 acres (79,789 hectares), and for that 10–year period was the second greatest acreage burned in any May, behind 2007. A total of 11,850 new wildfires were reported, which is 2,563 above the 2000–2009 average of 6,702 fires. This is the second greatest number of fires in May, behind 2000. Average fire size in May 2009 was 33.7 acres (13.6 hectares) burned per fire. This value is 3.9 acres (1.6 hectares) per fire above the 2000–2009 average fire size of 29.8 acres (12.1 hectares) per fire.

For the period from January 1st through May 29th, total year–to–date acreage burned was 1,377,310 acres (557,378 hectares), which was 411,182 acres (166,399 hectares) above the 2000–2009 average of 966,128 acres (390,978 hectares), and the third greatest amount of acreage burned for the period since 1999. The year–to–date (January – May) number of fires was 41,328, or 10,077 fires above the 2000–2009 average of 31,251 fires. This ranks 2009 as the highest year–to–date number of fires over the past decade. Combined, the year to date number of fires and acreage burned yields an average of 33.3 acres (10.4 hectares) per fire.

The cumulative number of fires and acres burned to date in 2009 have consistently exceeded their respective 10–year averages. Early–year activity was only slightly above the long term average for both variables, but since that time, the number of wildfires above the 2000–2009 average has steadily increased. Several large fires in April served to dramatically increase the 2009 year–to–date acreage burned relative to its long–term average.

According to the U.S. Drought Monitor, the heavy rains and flooding experienced over Florida toward the end of May alleviated much of the drought and associated fire danger that had been building across the state. Severe to exceptional drought did however continue to plague southern Texas throughout the month, while moderate to severe drought remained in place across much of California, Nevada and adjacent parts of the western United States.

The U.S. Forest Service (USFS) – Wildland Fire Assessment System, indicated that observed fire danger had decreased dramatically in New England and across much of the Southwest U.S. during May. At the start of the month, high to extreme fire danger existed from Maine southwestward into central New York, and in the southwestern U.S. from western Texas northward to southern Wyoming and west into California. In mid–May, no area of the nation was under extreme fire danger, although much of the Southwest remained under high to very high danger. May closed with high to very high danger confined to small areas in places such as the southern Southwest U.S., the Mississippi Delta, northern parts of Washington and Idaho, Maine and southern Minnesota.

Fire Danger Maps:

2009 Wildfire Statistics

(Source: NIFC)
Year–To–Date Totals as of May 1st Nationwide Number of Fires Nationwide Number of Acres Burned
05/29/2009 41,328 1,377,310
05/29/2008 24,927 1,432,503
05/29/2007 34,021 864,004
05/29/2006 39,996 2,452,783
05/29/2005 21,985 344,365
05/29/2004 30,726 484,163
05/29/2003 19,809 383,281
05/29/2002 28,383 696,126
05/29/2001 31,472 599,673
05/29/2000 39,865 1,027,072
5–yr average
(2005 – 2009)
32,451 1,294,193
10–yr average
(2000 – 2009)
31,251 966,128

While critically low 10–hour dead fuel moisture levels continued to plague much of the western United States during May, rainfall in the early part of the month improved conditions in New England and across much of the Southeast. However, by the middle of the month, low fuel moisture levels had spread into the Plains states and the upper Midwest. At the end of May, critically low to moderate 10–hr fuel moisture levels were present across much of the nation.

The 100–hour and 1000–hour fuel moisture levels were generally low across much of the west–central United States at the beginning of May, with critically dry 100–hr moisture levels in the Southwest. Low 100–hr moisture levels also existed throughout the eastern U.S. from Florida to Maine. Mid–May brought deteriorating moisture levels to much of the Plains and upper Midwest. By the end of May, higher levels of 100–hr fuel moisture had largely retreated to Florida, the Appalachian Mountains and New England, leaving the rest of the nation with moderate to critically low larger fuel moisture levels.

10–hour Fuel Moisture Maps:

100–hr Fuel Moisture Maps:

1000–hr Fuel Moisture Maps:

The Keetch–Byram Drought Index (KBDI), a widely used drought index for fire risk, showed critically dry conditions in southern Texas, central Nevada, and southern Florida at the beginning of May. The KDBI showed little spatial change throughout the month for most of the nation. However, rains toward the end of May helped to lower KBDI levels in most of the areas that had experienced high to extreme KBDI levels earlier in the month.

KBDI Maps:

Citing This Report

NOAA National Climatic Data Center, State of the Climate: Wildfires for May 2009, published online June 2009, retrieved on July 25, 2014 from http://www.ncdc.noaa.gov/sotc/fire/2009/5.