June 5, 2009

In a Nutshell: May 2009 Precipitation: Most sites reported below normal precipitation; but it rained somewhere in the state on 19 days. Most Precipitation: 7.71 inches at Culbertson (Hitchcock County). Most Precipitation in 24 hours: 3.55 inches at Haigler (Dundy County) on May 26. High: 99°F at Valentine May 19 and at Kilgore May 20. Low: 25°F at Chadron May 16. Tornado: Only one touched down in Nebraska in May, which is below normal.

May precipitation in inches. (Source: High Plains Regional Climate Center.)

Departure from normal temperatures (F). (Source: High Plains Regional Climate Center.)

Below normal precipitation and average temperatures were the norm across most of Nebraska in May. Most precipitation events were light -less than 1 inch and scattered- allowing corn and soybean planting to proceed with few interruptions. Corn planting was virtually completed by mid-May, and most soybean fields were planted by the end of May.

Wet conditions last October and December built generous soil moisture reserves for this year's crop, providing ample moisture for excellent stand emergence. However, with little rain in May, crops are using stored soil moisture quicker than normal, increasing the likelihood of drought conditions this summer.

Precipitation Record

Southwest Nebraska was the only climate district reporting above normal moisture with many sites having 100-150% of normal. The eastern third of Nebraska had exceptionally dry conditions with 10- 60% of normal precipitation.

This was the fifth consecutive month of below normal moisture for the eastern third of the state. Accumulated year-to-date deficits approached 7 inches in some areas, with the remainder reporting deficits 4-6 inches below normal.

For January 1 - May 31:

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• the Lincoln Airport received 3.89 inches, the second driest in the 44 years of available data;
• the Norfolk Airport received 4.54 inches. the 12th driest in the last 100 years; and
• Omaha Eppley Airport recorded 5.63 inches, the fifth driest in the last 74 years.

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Precipitation was reported somewhere within the state on 19 days. The most significant event occurred May 26 across the southwest climate district. Twenty-four hour totals exceeding 1.50 inches were common, with at least eight sites reporting more than 2 inches. The heaviest rainfall was in Chase, Hitchcock, and Frontier counties.

NeRAIN Expanded Picture

Our reporting network didn't capture many of the isolated thunderstorms which occurred in May. These were captured by the NeRAIN Project, which consists of nearly 1000 volunteers across the state who report weather data. While NeRAIN reports aren't "official" records, they do capture the finer details of individual storm events and fill in gaps in areas where there aren't official weather stations.

Using the NeRAIN data, several locations reported 24-hour precipitation totals exceeding 1.5 inches. These occurred on May 1 (south central), May 13 (east central), May 16 (southeast), May 21 (north central), May 23 (north central), May 24 (southwest, south central, east central), May 25 (central, south central, southeast), May 26 (southwest, west central), and May 27 (southwest, south central, southeast).

Temperature

May temperatures generally were normal, with averages for most of the 153 reporting sites falling within one degree of normal. Only a couple sites had highs exceeding 85°F. Generally, average temperatures for the northern third of the state were below normal, with the central third normal, and the southern third slightly above normal. The warmest period was May 18-20 and the coolest was May 14-16.

Hard freeze conditions (below 28°F) were reported at 12 locations in the Panhandle and western Sandhills (north central Nebraska) on May 14. Light to moderate frost (29°F - 32°F) was reported across much of the Panhandle, north central, and northeast Nebraska several times from May 11 to May 16.

Severe Weather

Only one tornado touchdown was confirmed by the National Weather Service in Nebraska during May. The EF0 tornado touched down 17 miles south-southwest of Mullen on May 12. In a typical year, approximately two-thirds of tornado touchdowns occur in May and June in Nebraska. The North Platte National Weather Service reports that May had the fewest severe weather alerts since 1992.

Al Dutcher
State Climatologist