May 2007 Climatic Summary

The first week of May was dominated by a powerful upper level storm system. Seasonal temperatures and scattered showers occurred the first three days of May with heavy rains falling across the region May 4 through May 6. Rainfall totals averaged 2.5 to 4.0 inches across northeastern Wyoming and western South Dakota. The 3.95 inches that fell in Interior on May 5 was the most rainfall ever there on a given day. Severe weather was also associated with this system. Isolated severe thunderstorms in south central South Dakota on May 4 produced wind gusts to 60 miles per hour. On May 5 widespread severe weather occurred across southwestern and south central South Dakota with large hail to the size of golf balls reported. Dry and warm weather returned on May 8 and continued through May 12. From May 13 through the end of the month temperatures averaged 3 to 5 degrees above normal. It was an active period with several rounds of severe weather across the region.
Severe weather struck on May 13 with damaging winds being reported mainly in northeastern Wyoming and northwestern South Dakota. The strongest winds occurred in Buffalo where winds to 77 miles per hour were reported. On May 18 isolated severe weather occurred in northwestern South Dakota and in the northern Black Hills where penny size hail was reported. Hail to the size of half dollars was reported again on May 19 in the central Black Hills. On May 20 a tornado touched down 15 miles south of Gillette, while large hail to the size of golf balls fell across the central Black Hills and southwestern South Dakota. On May 21 hail to the size of Ping Pong balls were reported across central portions of western South Dakota. On May 25 severe weather broke out again across central and south central South Dakota with hail to the size of quarters being reported. On May 28 a major severe weather event broke out across northeastern Wyoming, the Black Hills and central South Dakota. A tornado touched down 12 miles northwest of Wright in Campbell county Wyoming. Large hail to the size of golf balls were reported along with damaging winds up to 75 miles per hour.
May was a warm month with temperatures averaging 3 to 5 degrees above normal. All locations reported above normal temperatures. Averages ranged from 5.7 degrees above normal at Sundance in northeastern Wyoming to 0.6 degrees above normal at Colony in northeastern Wyoming.
May was a very wet month with precipitation near or above normal over all but southwestern South Dakota. The wet spots were in northwestern South Dakota, the northern Black Hills and northeastern Wyoming where precipitation averaged 150 to 200 percent of normal. In southwestern South Dakota it was another dry month as only 50 to 70 percent of normal precipitation fell. Elsewhere on the plains of western South Dakota precipitation averaged 125 to 150 percent of normal.  Precipitation ranged from 273 percent of normal at Gillette 4SE in northeastern Wyoming where 8.05 inches of rain fell and 201 percent of normal in Deadwood 2NE where 9.41 inches of rain fell  to 47 percent of normal at Ardmore 2N where only 1.35 inches of rainfall fell. The rainfall surplus for the month averaged 0.85 inches.
Snowfall in May was confined to a few flurries in the higher elevations of the Black Hills and an inch or less across far southern Campbell county in northeastern Wyoming.


Temperature Data Rapid City   Lead   Gillette  
  Temperature Date Temperature Date Temperature  Date
Maximum Temperature 91 degrees 13th 82 degrees 13th 85 degrees 12th
Minimum Temperature 33 degrees 24th 32 degrees 27th 32 degrees 15th,  24th
Precipitation Data Rapid City   Lead   Gillette  
Monthly  Data Amount Data Amount Date Amount Date
Precipitation 2.93 inches   6.27 inches   8.05 inches  
Snowfall 0.0 inhces   0.0 inhces   0.0 inhces  
Daily Data            
Maximum Precipitation 1.10 inches 5th 2.30 inches 5th 2.00 inches 6th
Maximum Snowfall 0.0 inhces   0.0 inhces   0.0 inhces  


Temperature Data   Western South Dakota     Northeastern Wyoming  
  Temperature Site Date Temperature Site Date
Maximum Temperature 96 degrees Ardmore 2N 13th 91 degrees Newcastle 14th
Minimum Temperature 27 degrees Pactola Dam 24th 26 degrees Dillinger   
 Upton 14ENE
         4th                     24th, 25th 
Precipitation Data   Western South Dakota     Northeastern Wyoming  
Monthly Data Amount Site Date Amount Site Date
Maximum Precipitation 9.41 inches Deadwood 2NE   8.05 inches Gillette 4 SE  
Minimum Precipitation 1.35 inches Ardmore 2N   2.43 inches Colony  
Maximum Snowfall 0.0 inches     0.0 inches    
Minimum Snowfall 0.0 inches     0.0 inches    
Daily Data            
Maximum Precipitation 3.95 inches Interior 3NE 5th 3.00 inches Rockypoint 1N 6th
Maximum Snowfall 0.0 inhces     0.0 inhces    


Interior 3NE 5/5/2007 3.95 inches of rainfall 2.75 inches 5/27/1996
Maurine 10SW 5/6/2007 1.94 inches of rainfall 1.86 inches 5/9/1995

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