April Checks In at No. 3 on All-Time Warmest List for U.S.

By Andrew Freedman

Following the warmest March on record, the contiguous U.S. had its third-warmest April, and the year-to-date is running warmer than any other since record keeping began in 1895, the National Oceanic and Atmospheric Administration (NOAA) announced today. 

The 12-month period of May 2011 to April 2012 had a nationally averaged temperature of 2.8°F above the 1901-2000 average, NOAA said, making it the warmest such period on record. That timeframe has also encompassed the second-hottest summer, fourth-warmest winter, and warmest March. The top ten warmest 12-month periods in the Lower 48 states have all occurred since 1999.

Locations where monthly record high temperatures were set during April 2012. The colors indicate the magnitude by which the previous record was exceeded. Credit: NOAA.

The year-to-date has also been unusually warm, departing from the long-term average by 5.4°F, a trend that was influenced by the unprecedented March heat wave, and warm spells during April as well. Twenty-six states east of the Rockies were record warm for the January-to-April period, while 17 more states had temperatures for the period among their 10 warmest. North Dakota exceeded its average for the year-to-date by 10.4°F, the largest margin ever recorded, and the entire Upper Midwest region was 8.7°F above average during the same timeframe.

In a special report on the 2012 warmth, NOAA detailed cities that have experienced their warmest years-to-date as well, which range span a wide region from Boston to Amarillo, Texas. 

During April, nine states in the Central and Northeast regions had temperatures ranking in their top 10 warmest for the month. More than 300 locations in the U.S. had a daily warm temperature that was the warmest on record for April, according to data from the NOAA National Climatic Data Center (NCDC). Many of the monthly records were broken by a large margin of well over 1°F. Many of these records were concentrated in the Rocky Mountains and Southern Plains, with 50 of these records set in Texas.

According to NOAA, a decade of warmer than average Aprils has eliminated most of the highest monthly maximum temperature records that had been set during the 20th Century. 

Remarkably, eight states — Illinois, Indiana, Kentucky, Michigan, Wisconsin, Ohio, Pennsylvania, and West Virginia — had a cooler April compared to March, even though April was still warmer than average in those states. Many observing stations across the Midwest and Ohio Valley pulled off the rare feat of having a cooler April compared to March, which in some cases had never happened before.

The U.S. has been drier than average so far during 2012, and as of May 1, 38.2 percent of the Lower 48 states were experiencing drought conditions, which is up from about 32 percent at the start of the year. While the Texas drought has eased, drought conditions have developed in parts of the Southeast, Mid-Atlantic and Northeast, as well as the Interior West. Maryland and Delaware both had record dry conditions during the first four months of 2012.

Thanks to widespread record daytime high temperatures and record warm overnight lows, NOAA's Climate Extremes Index — which measures the highest and lowest 10 percent of extremes in temperature, precipitation, drought and tropical cyclones across the contiguous U.S.—was more than twice the average value during the January-April period. 

Compared to April 2011, the country was lucky when it came to tornadoes. There were 228 preliminary tornado reports during April 2012, compared to more than 750 confirmed tornadoes during the same month last year. April 2011 ranks as the busiest tornado month since reliable tornado records began in 1950.