May 2010 Climate Summary

For a printable version of the climate summary which includes more figures, data tables, and state summaries, click here. 

Temperature Summary

May 2010 was cooler than normal across the Region.  For most of the month, average temperatures were below normal, but the end of the month was characterized by above normal temperatures.  Despite the warm temperatures, temperature departures were below normal overall.  The largest temperature departures occurred in eastern North Dakota and Wyoming where temperature departures were 4-8 degrees F (2.2-4.4 degrees C) below normal.  Many locations in Wyoming ranked in the top 10 coolest Mays on record.  Worland, Wyoming was this month’s record breaking location with an average temperature of 50.0 degrees F (10.0 degrees C) which was 7.7 degrees F (4.3 degrees C) below normal.  This beat out the old record of 52.4 degrees F (11.3 degrees C) recorded in May 1983 (period of record 1960-2010).

Precipitation Summary

Precipitation was variable over the Region this month.  A large swath of below normal precipitation stretched from the four corners region northeast through portions of Nebraska, Kansas, and South Dakota.  Western Wyoming, where drought conditions are ongoing also received below normal precipitation.  Areas receiving at least 150 percent of normal include much of North Dakota, western and central South Dakota, central Wyoming, and pockets of Kansas.  The precipitation in south central Kansas and western North Dakota helped eliminate the abnormally dry conditions which had developed last month.   

Like last month, weather ranging from snow to tornadoes affected parts of the Region.  One strong storm occurred May 11-12 and brought snow to Wyoming, Colorado, and Nebraska.  In central Wyoming, unofficial reports indicate that up to 40 inches (101.60 cm) of snow fell on the east slopes of the Wind River and southern Absaroka mountains.  The late season snowstorm also bumped Scottsbluff, Nebraska up to the snowiest season on record and Cheyenne, Wyoming up to the second snowiest season on record.  Scottsbluff, Nebraska received 82.2 inches (208.79 cm) of snow which beat out the old record of 78.5 inches (199.39 cm) recorded during the 1979-1980 snow season (period of record 1893-2010).  Cheyenne, Wyoming received 103.4 inches (262.64 cm) of snow this season which came in second to the record 121.5 inches (308.61 cm) of snow received in the 1979-1980 snow season (period of record 1883-2010).  

Another strong storm occurred May 24th and brought severe weather to the Dakotas, Nebraska, and Kansas.  Multiple tornadoes were reported and one EF-2 tornado destroyed an elementary school in northwest South Dakota.  In addition, 4.25 inch hail was reported in the panhandle of Nebraska, high winds caused damage in Alliance, Nebraska, and flooding was reported along the White River in Nebraska.

Climate Outlook

El Niño conditions are currently transitioning to El Niño Southern Oscillation (ENSO) neutral conditions at this time as indicated by decreasing sea surface temperatures in the Pacific Ocean.  Models are indicating a possibility of La Niña developing later in 2010.  The temperature outlook indicates a higher probability of below normal temperatures for the majority of the Region including the Dakotas, Nebraska, Kansas, and northeastern Wyoming.  The western half of Colorado and the far southwestern corner of Wyoming have a higher probability for above normal temperatures.  Equal chances of above, near, or below normal temperatures are predicted elsewhere.  The precipitation outlook indicates a higher probability of above normal precipitation for the Dakotas, Nebraska, Kansas, eastern Wyoming, and the eastern half of Colorado.  Equal chances of above, near, or below normal precipitation are predicted elsewhere in the Region.  More information about these forecasts can be found here.

Drought Watch

This month, abnormally dry conditions (D0) were eliminated in central Kansas and the northwest corner of North Dakota.  Although abnormally dry to moderate drought conditions (D0-D2) remain in western Wyoming, much of the drought conditions in central Wyoming have been eliminated or reduced in intensity due to late season snow storms.  For example, snow totals for the May 11-12 snowstorm in central Wyoming were upward of 40 inches in some locations.  According to the U.S. Seasonal Drought Outlook released May 20th, the drought conditions in northwestern Colorado and western Wyoming are expected to improve through August 2010.