The spring season (March-May) of 2000, as well as the year-to-date (January-May), was the warmest on record for the United States, according to statistics calculated by NOAA's scientists working from the world's largest statistical weather database. The electronic database at NOAA's National Climatic Data Center in Asheville, N.C., goes back through 106 years of record keeping.

The U.S. national spring season temperatures averaged 55.5 degrees Fahrenheit, 0.4 degrees Fahrenheit warmer than the previous record set in 1910, based on preliminary data. This was 3.3 degrees Fahrenheit warmer than the 1895-1999 long-term mean temperature of 52.2 degrees Fahrenheit. For the three-month period, over 64 percent of the country averaged much warmer than normal, while less than one percent averaged much cooler than normal.

During this spring season, every state in the continental U.S. was warmer than its long-term average. It was the warmest spring on record for Texas, second warmest spring since 1895 for New Mexico, and the third warmest spring on record for Nevada. Twenty additional states ranked within the top ten warmest spring seasons on record.

The extremely warm temperatures contributed to worsening drought conditions in many areas of the country. Parts of the Southeast, Midwest, and Southwest continue to experience severe to extreme drought, causing crop damage and creating the need for water rationing in many areas. Twelve states averaged drier than normal for the spring season. Florida reported its fourth driest spring on record, while Missouri had its eighth driest spring since 1895.

With an average five-month temperature of 48.5 degrees Fahrenheit, the year-to-date, January-May, 2000, is also the warmest such period on record. The old record of 47.4 degrees Fahrenheit was set in 1986. For the January-May period, over 76 percent of the country was much warmer than normal, while less than one percent of the country was much cooler than normal.

For the year-to-date, every state in the continental U.S. was warmer than its long-term average. It was the warmest January-May period on record for Arizona, New Mexico and Texas, and the second warmest year-to-date on record for Colorado, Nebraska, Nevada, Oklahoma and Utah. Twenty-one other states ranked within their ten warmest ever.

Overall dryness persisted in the southern tier of states and portions of the Mississippi Valley. It was the third driest January-May period on record for Florida, eighth driest for Mississippi, and tenth driest for Louisiana. In all, 14 states were drier than normal for the January-May period. For the 48 contiguous states, January-May was the 35th driest such period since 1895.

Although many areas endured extremely dry conditions throughout the first five months of the year, the Northeast received much above normal precipitation. New York noted its second wettest such period on record, and Vermont had the third wettest January-May period.

In addition to NOAA's surface temperature statistics, satellite data provided by scientists at NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville also indicated the presence of extremely warm temperatures in the lower half of the atmosphere (lowest 8km or 26,200 feet of the atmosphere) over the U.S. The Microwave Sounding Unit on-board NOAA's TIROS-N polar-orbiting satellite measured record warm temperatures during the May, spring, and January through May year-to-date periods. The average lower tropospheric temperature over the continental U.S. was 3.53 degrees Fahrenheit above the 1979-1998 long-term mean in May, and 1.49 degrees Fahrenheit warmer than the previous record from May 1996. The average spring temperature anomaly was 2.0 degrees Fahrenheit and the year-to-date temperature was 2.12 degrees Fahrenheit above the long-term mean, both breaking previous records set in 1989.

Global Data:

Global temperatures were also very high during the Northern Hemisphere spring season. This was the 24th consecutive March-May period in which global temperatures were warmer than the 1880-1999 long-term mean. The combined land and ocean surface temperature anomaly of +0.86 degrees Fahrenheit tied 1990 as the second warmest such period on record. Land surface temperatures also tied 1990 as the second warmest, 1.73 degrees Fahrenheit above average. The only March-May season with higher temperatures occurred during the 1997/1998 El Niño episode. As in recent seasons, temperatures in the Northern Hemisphere north of 20 degrees North remained abnormally warm while temperatures in the tropics (20°N - 20°S) continued to be held down by the persistence of the cold phase of El Niño (La Niña).

Data from the Microwave Sounding Unit indicates that, within the tropics, the average temperature in the lower half of the atmosphere (lowest 8km or 26,200 feet of the atmosphere) was the second coldest on record for the March-May season, -0.85 degrees Fahrenheit below the 1979-1998 average. Conversely, in the Northern Hemisphere Extratropics (90°N - 20°N) the average temperature was +0.59 degrees Fahrenheit above the 20-year average, making March-May 2000 the fifth warmest such period within this region. Primarily because of the much colder than normal temperatures in the tropics, the globally averaged temperature in the lower half of the atmosphere was -0.07 degrees Fahrenheit below average, continuing the trend of near-record surface temperatures with much more moderate temperatures aloft.

The statistics for May, the spring, and the year-to-date are online atthe following Web site: Climate of 2000 May in Historical Perspective