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State Climate Summaries

ARKANSAS

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Arkansas State Capitol Building
Photo by Mike Rastiello

ARKANSAS

Arkansas is located in the interior southern United States. The state is close, but not adjacent to the Gulf of Mexico, resulting in a climate that is largely characterized by moderately large variations in temperature and abundant precipitation. Summers are hot and humid, while winters are typically short and cool, with occasional episodes of cold Arctic air. A diagonal line, cutting across the state from northeast and southwest, demarcates the topography of Arkansas. The area northwest of that line includes the Arkansas Ozark Mountains and is generally higher in elevation. Thus, temperatures are generally cooler in this area, particularly in the Boston Mountains portion of the range where some peaks exceed 2500 feet. For example, the average high temperature in July is 90°F at Newport (elevation of 230 feet) in the northeast, while the average high temperature is 82°F at Deer (elevation of 2375 feet) in the northwest. Average low temperatures in January range from 20–25°F in the northwestern tip to 25–30°F in the northeast to 30–35°F in the southwestern portion of the state. Precipitation is abundant throughout the year. Heavy rains can produce totals in excess of 10 inches. Winter and spring are the wettest seasons. The year 1963 was the driest year on record since 1895 with a statewide average of 32.8 inches of precipitation; while the wettest year recorded was 2009, with an average of 72.2 inches of precipitation. Historical extreme temperatures for the state range from a record 120°F in Ozark, set on August 10, 1936 to a record low of -29°F in Gravette set on February 13, 1905.

 

Figure 1

Observed and Projected Temperature Change

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Observed and projected changes (compared to the 1901-1960 average) in near-surface air temperature for Arkansas. Observed data are for 1900–2014. Projected changes for 2006-2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions). Temperatures in Arkansas (orange line) were warmest in the 1930s, coolest in the 1960s through the 1980s. Temperatures have risen about 1.5°F since the 1960s, but have not exceeded the levels of the 1930s. Shading indicates the range of annual temperatures from the set of models. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Historically unprecedented warming is projected during the 21st century. Less warming is expected under a lower emissions future (the coldest years being about as warm as the hottest year in the historical record; green shading) and more warming under a higher emissions future (the hottest years being about 12°F warmer than the hottest year in the historical record. Source: CICS-NC and NOAA NCEI.

Arkansas has not seen a significant overall increase in temperature since the early 20th century—similar to the rest of the southeastern United States. Arkansas warmed from the early 20th century into the 1930s followed by a period of cooling into the 1970s of about 2°F. Gradual warming has occurred since the 1970s (at about the same rate as the rest of the United States), but the recent higher temperatures (slightly above the long-term average) have not exceeded those of the 1930s (Figure 1). Because of the large cooling that occurred in the middle of the 20th century, the southeastern United States is one of the few locations globally that has not experienced overall warming since 1900, while the United States as a whole has warmed by about 1.5°F. The United States as a whole also cooled from the 1930s into the 1960s, but not by nearly as much as Arkansas.

The number of extremely hot days (maximum temperature above 100°F) peaked during the 1930s and early 1950s, and both time periods were accompanied by drought (Figure 2a). Since the mid-1950s, the number of such days has been near or below average. Although the number of extremely hot days has not been unusual, mean summer temperatures and very warm nights (minimum temperature above 75°F) during 2010–2014 equaled or exceeded previous record levels, primarily because of an unprecedented warm string of three summers (2010-2012). For 2010–2014, the number of very warm nights was double the long-term average (Figure 3) and annual average summer temperatures were 1.5°F above average (Figure 4), matching or exceeding records set in the 1930s and 1950s. The number of very warm nights in 2015 and 2016 were also well above the long-term average. A winter warming trend is reflected in a below average number of very cold nights (minimum temperature below 0°F) over the past two decades (1990–2014) (Figure 2b).

Figure 2

Figure 2a

 

2a

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Figure 2b

 

2b

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Figure 2c

 

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Figure 2d

 

2d

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Figure 2: The observed (a) number of extremely hot days (maximum temperature above 100°F), (b) very cold nights (minimum temperature below 0°F), (c) annual precipitation, and (d) summer precipitation, averaged over 5-year periods. The values in Figures 2a and 2b are averages from 16 long-term reporting stations. The values in Figures 2c and 2d are from NCEI’s version 2 climate division data set. The dark horizontal lines represent the long-term average. The number of very hot days and very cold nights have remained below average for the past two decades (1990–2014). While annual precipitation has generally been near or above the long-term average, average summer precipitation has been below average since the 1990s. Source: CICS-NC and NOAA NCEI.

 

Observed Number of Very Warm Nights

Observed Number of Very Warm Nights

Figure 3: The observed number of very warm nights (annual number of days with minimum temperature above 75°F) for 1900–2014, averaged over 5-year periods; these values are averages from 16 long-term reporting stations. The number of very warm nights has generally been above average since 1995, with a record number of such events occurring during the most recent 5-year period (2010–2014) because of very high values in 2010, 2011, and 2012. The dark horizontal line is the long-term average of about 8 days per year per station. Source: CICS-NC and NOAA NCEI.

 

Observed Summer Temperature

Observed Summer Temperature

Figure 4: The observed annual summer temperatures for 1895–2014, averaged over 5-year periods; these values are from NCEI’s version 2 climate division data set. Average summer temperatures have typically been about average since 1980, with the exception of much above temperatures the most recent 5-year period (2010–2014), because of very warm summers in 2010 (4th warmest), 2011 (tied for warmest), and 2012 (10th warmest). The dark horizontal line is the long-term average of 78.8°F. Source: CICS-NC and NOAA NCEI.

There is no overall trend in average annual precipitation in Arkansas (Figure 2c). There is also no trend in the annual number of extreme precipitation events, although the highest 5-year average number occurred in 2005–2009, with the number (1.6 days per year) about 40% above the long-term average (1.1 days per year) (Figure 5) because of exceptionally high values in 2008 (3rd highest year since 1900) and 2009 (highest year); the 2nd highest annual value was in 2015. Average annual summer precipitation has been near or below average since the 1980s (Figure 2d). Water levels in the Alluvial Aquifer, the primary source of groundwater in Arkansas, have declined by about 3.7 feet from 2004 to 2014. A vitally important characteristic of the precipitation climatology is its high variability. In recent years, severe drought episodes occurred in the state during 2005–2007 and again during 2010–2012, interrupted by the wettest year on record in 2009 and followed by the fifth wettest in 2015. The driest 5-year period was 1952–1956 with annual average precipitation of 41.97 inches and the wettest was 1990–1994 with 56.62 inches. Arkansas was one of the hardest hit southeastern states during the 2012 drought. Each of the state’s 75 counties received a drought-related disaster declaration. Since the creation of the United States Drought Monitor Map in 2000, Arkansas has only been completely drought-free for approximately 39% of the time (2000–2014) and has had at least 50% or more drought coverage for approximately 19% of the time during that same period.

 

Observed Number of Extreme Precipitation Events

Observed Number of Extreme Precipitation Events

Figure 5: The observed number of extreme precipitation events (annual number of events with greater than 3 inches) for 1900–2014, averaged over 5-year periods; these values are averages from 22 long-term reporting stations. There is no long-term trend, with the highest number of such events occurring during 2005–2009 because of very high values in 2008 and 2009. The dark horizontal line is the long-term average of a little over 1 day per year per station. Source: CICS-NC and NOAA NCEI.

Extreme weather events in Arkansas include severe thunderstorms, tornadoes, flood-producing heavy rain, and winter ice storms. The most destructive flood in United States history, the Mississippi River Floods of 1927, affected Arkansas by inundating 36 out of 75 counties across the state, with floodwaters as deep as 30 feet in some places. This flood was a result of persistent heavy rainfall across the central United States from August 1926 through the spring of 1927. The unprecedented amounts of rainwater run-off overwhelmed the protective levees. This event led to the Flood Control Act of 1928, allowing for federal government authority to contain the Mississippi River and mitigation efforts that have helped to prevent future flooding events of this magnitude. In May of 2011, floods submerged more than one million acres of Arkansas farmland, costing the state’s agricultural industry approximately $500 million in damages. In the most recent decade, a total of 23 FEMA disaster declarations have been awarded to the state, the majority of which (16 declarations) were for severe thunderstorms, tornadoes, and flooding. Arkansas regularly experiences tornadoes. Over the past 30 years (1985–2014) Arkansas has averaged approximately 32 tornadoes and 5 tornado fatalities per year. The Super Tuesday Tornado Outbreak of February 2008 resulted in 57 fatalities in four states, the second largest number of tornado fatalities since the May 31, 1985 outbreak (88 fatalities). During this tornado outbreak, Arkansas experienced a long-track (122 miles) EF4 tornado, the longest track on record since 1950, causing an estimated $102 million in damages across central and northern Arkansas and 14 fatalities.

Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century (Figure 1). Even under a pathway of lower greenhouse gas emissions, average annual temperatures are projected to most likely exceed historical record levels by the middle of the 21st century. However, there is a large range of temperature increases under both pathways, and under the lower pathway, a few projections are only slightly warmer than historical records. Heat wave intensity is projected to increase, while cold waves are projected to be less severe.

Winter precipitation is projected to increase in Arkansas by mid-century (Figure 6). In the other seasons, precipitation changes are uncertain. Higher temperatures will increase the rate of loss of soil moisture during dry spells. As a result, naturally occurring droughts are projected to be more intense.

 

Projected Change in Winter Precipitation

Projected Change in Winter Precipitation

Figure 6: Projected changes (%) in winter precipitation for the middle of the 21st century relative to the late 20th century under a higher emissions pathway. Hatching represents areas where the majority of climate models indicate a statistically significant change. Arkansas is part of a large area of projected increases in winter precipitation across the United States. Source: CICS-NC, NOAA NCEI, and NEMAC.

Lead Authors:
Jennifer Runkle, Kenneth E. Kunkel
Contributing Authors:
Sarah Champion, Brooke Stewart, and David Easterling
Recommended Citation:
Runkle, J., K. Kunkel, S. Champion, B. Stewart, and D. Easterling, 2017: Arkansas State Summary. NOAA Technical Report NESDIS 149-AR, 4 pp.

Resources

  1. NOAA, cited 2016: Climate of Arkansas, National Oceanic and Atmospheric Administration. [Availableonline at https://www.ncdc.noaa.gov/climatenormals/clim60/states/Clim_AR_01.pdf]
  2. Thomas R.K., J.M. Melillo, and T.C. Peterson, eds., 2009: GlobalClimateChangeImpactsin the United States, Cambridge University Press, 196pp. [Available online at https://downloads.globalchange.gov/usimpacts/pdfs/climate-impacts-report.pdf]
  3. NOAA, cited 2016: Summary - The May 31, 1985 tornado outbreak (25th Anniversary), NationalOceanic and Atmospheric Administration. [Available online at http://www.erh.noaa.gov/ctp/features/TornadoOutbreak_May1985/TornadoOutbreak_May1985_Summary.pdf]
  4. NOAA, cited 2016: Flooding in Mississippi, Mississippi River Floods of 1927, NationalOceanic and Atmospheric Administration. [Available online at http://www.floodsafety.noaa.gov/states/ms-flood.shtml]
  5. The Encyclopedia of ArkansasHistory and Culture, cited 2016: Flood of 1927, The Central Arkansas Library System. [Available online at http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2202]
  6. NOAA, cited 2015: State Climate Extremes Committee (SCEC), Records, National Oceanic and Atmospheric Administration NationalCenters for Environmental Information. [Available online at http://www.ncdc.noaa.gov/extremes/scec/records]
  7. NOAA, cited 2015: Storm Prediction Center WCM Page. National Oceanic and Atmospheric Administration, Storm Prediction Center. [Available online at http://www.spc.noaa.gov/wcm/]
  8. NDMC, cited 2017:  Tabular data archive: Percent area in U.S. drought monitor categories, retrieved January 3, 2017, The National Drought Mitigation Center. [Available online at http://droughtmonitor.unl.edu/MapsAndData/DataTables.aspx]
  9. Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, C.E. Konrad II, C.M. Fuhrman, B.D. Keim, M.C. Kruk, A. Billet, H. Needham, M. Schafer, and J.G. Dobson, 2013: Regional Climate Trends and Scenariosfor the U.S. National Climate Assessment. Part 2. Climateof the Southeast U.S., NOAA Technical Report NESDIS 142-2, 94 pp. [Available online at https://www.nesdis.noaa.gov/content/technical-reports]
  10. Midwestern Regional Climate Center, cited 2016: “(1981-2010) Maps of griddeddata long-term averages; Average Min Temp – Arkansas.” [Available online at http://mrcc.isws.illinois.edu/CLIMATE/]
  11. Office of the Arkansas State Climatologist, cited 2016: Climate of Arkansas. [Available online at http://www.climate.ar.gov/Climate%20Intro.pdf]
  12. 20. FEMA, cited 2016: Disaster declarations for Arkansas, Federal Emergency Management Agency. [Available online at http://www.fema.gov/disasters/grid/state-tribal-government/61]
  13. NASA, cited 2016: Images of May2011 flooding in Arkansas. NASA images courtesy of MODIS Rapid Response Team, GoddardSpace Flight Center, National Aeronautics and Space Administration. [Available online at http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50561]
  14. NWS, cited 2016: Super Tuesday tornadoes - National Weather Service. [Available online at http://www.nws.noaa.gov/om/assessments/pdfs/super_tuesday.pdf]
  15. NOAA, cited 2016: Tornadoes on February5, 2008 - Little Rock, AR, NationalOceanic and Atmospheric Administration. [Available online at http://www.srh.noaa.gov/lzk/?n=svr0208yr.html]
  16. USDA, cited 2016: 2012 Arkansas drought information, United States Department of Agriculture.  [Availableonline at http://www.nrcs.usda.gov/wps/portal/nrcs/detail/ar/home/?cid=nrcs142p2_034977]
  17. Arkansas Groundwater Protection and Management Report, 2014: A Supplement to the Arkansas Water Plan, 92pp. [Available online at https://static.ark.org/eeuploads/anrc/2015_Report_Final_Commpressed.pdf]
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