Climate Monitoring / Climate of 2007 / April / Help

Climate of 2007 - April in Historical Perspective

National Climatic Data Center
15 May 2007

Contents of this Report:

Selected Global Significant Events for April 2007
page delimiter

Major Highlights


April began with a record cold outbreak that stretched from the Plains to the Southeast, bringing widespread crop and forest damage, but the contiguous U.S. temperature for the month as a whole was near average, according to scientists at NOAA's National Climatic Data Center in Asheville, N.C. Another month of drier-than-average conditions in the Southeast led to worsening drought conditions, while a strong Nor'easter brought severe flooding to parts of the Northeast. On a global scale, the April surface temperature was third warmest on record.

U.S. Temperature Highlights
For the contiguous U.S., last month's average temperature was 51.7°F(10.9°C), which was only 0.3°F (0.2°C) below the 20th century mean (based on preliminary data). The April temperature one year ago was the 2nd warmest on record, and the warmest April occurred in 1981, when the average temperature was 56.1°F (13.4°C). The coldest April occurred in 1920.

The month will be remembered most for the record cold outbreak from April 4-10, that produced widespread losses of fruit crops and damages to trees as far north as southern Illinois, as far west as Kansas and Texas, and encompassing all the southeastern states except mid-to-south Florida.

The lengthy duration of the cold outbreak, the large number of hours that remained below freezing, and strong winds in many areas, contributed to crop losses that could reach into the billions of dollars, according to agricultural experts. The magnitude of the outbreak is evident in the approximately 900 daily low temperature records that were set during the 4-day period.

The damaging effects of the record cold were made worse by record and near-record warmth in March that helped induce an earlier spring blossom, in some cases two weeks prior to crop development in 2006. For the month of March more than 2,500 daily record-high temperatures were set in the contiguous U.S., and it was the 2nd warmest March on record for the contiguous U.S..

According to NOAA's Air Resources Laboratory, Atmospheric Turbulence and Diffusion Division, forest ecosystem impacts from the cold, which killed vegetation and reduced tree leaf area, included a subsequent decrease in carbon dioxide uptake and more of the sun's energy being used for heating the atmosphere instead of evaporating water from vegetation.

Following its 3rd coldest March since statewide records began in 1918, Alaska had its 4th warmest April on record, with a temperature 5.96°F (3.3°C) above the 1971-2000 average.

U.S. Precipitation Highlights
The contiguous U.S. as a whole was drier than average in April. Abnormally dry conditions were widespread throughout the Southeast and Pacific Northwest, while much wetter than average conditions stretched along the Eastern Seaboard from Maine to New Jersey.

These wet conditions in the Northeast were in large part due to a strong Nor'easter that moved along the East Coast from the 15th-17th. Strong winds caused power outages that affected hundreds of thousands from South Carolina to Maine, while heavy rainfall generated flooding in areas of the Mid-Atlantic and Northeast. New York City had its second-rainiest day ever, with 7.57 inches on the 15th. The record for the heaviest daily rainfall is 8.28 inches set on September 23, 1882.

By contrast, drier than average conditions persisted across much of the Southeast. Precipitation for the first four months of the year was less than 50% of average in some areas, and severe drought stretched from western North Carolina and Tennessee to southern Mississippi by late in the month, with extreme drought affecting much of northern Alabama.

Extreme drought in southern Georgia led to the largest wildfire on record for the state, and several fires continued to burn in early May.

The water year (July 1-June 30) in Los Angeles continued to be the driest on record and severe to extreme drought stretched from the southern California coast to Arizona and north along the Sierra Nevada Mountains, where seasonal snowpack was less than 50% of average.

In early May, approximately 33 percent of the contiguous U.S. was in moderate to exceptional drought, according to the federal U.S. Drought Monitor. Other affected areas included much of Florida, parts of the northern Rockies and northern High Plains, and northern Minnesota.

Global Highlights
The combined global land and ocean surface temperature for April was the third warmest on record (1.19°F/0.66°C above the 20th century mean). For the January-April year-to-date period, the global surface temperature ranked warmest on record.

Separately, the global April land-surface temperature was the warmest on record. Monthly mean temperatures more than 5°F (3°C) above average covered large parts of Asia and Western Europe. The April ocean-surface temperature tied for seventh warmest in the 128-year period of record as neutral ENSO (El Niño-Southern Oscillation) conditions persisted in the equatorial Pacific (awaiting update to indices).

During the past century, global surface temperatures have increased at a rate near 0.11°F (0.06°C) per decade, but the rate of increase has been three times larger since 1976, or 0.32°F (0.18°C) per decade, with some of the largest temperature increases occurring in the high latitudes of the Northern Hemisphere.

page delimiter

Report Index

page delimiter

to the top Global Analysis

to the top Global Hazards and Significant Events

to the top National Overview

to the top United States Drought

page delimiter

Top of Page Top of Page

Climate Monitoring / Climate of 2007 / April / Help