The United States had the second warmest May and the warmest spring on record, the National Oceanographic and Atmospheric Administration says. NOAA scientists said the average temperature for the contiguous 48 U.S. states during May was 64.3 degrees Fahrenheit, 3.3 degrees above the long-term average, making it the second warmest May on record. The national average temperature for the March-May spring season was 57.1 degrees Fahrenheit, 5.2 degrees above the 1901-2000 long-term average, making it the warmest spring on record, a NOAA release said Friday. That surpassed the previous warmest spring -- in 1910 -- by 2 degrees. The high temperatures also contributed to the warmest year-to-date and the warmest 12-month period the nation has experienced since weather record-keeping began in 1895, NOAA said. The warm temperatures brought mixed precipitation totals across the United States, with the nation as a whole being drier than average, researchers said.