Hottest Spring Ever

A Crab Spider (family Thomisidae) imitating a flower bloom, awaiting prey.
Its arms are open wide waiting to strike.

Spring temperatures 2012 in the contiguous USA obliterated old records for hottest spring and most extreme season of any kind, said NOAA's National Climatic Data Center (NCDC). With the warmest March, third warmest April, and second warmest May, the March - April - May spring season was 5.2° F above average—the largest temperature departure from average of any season on record for the contiguous United States. What's truly remarkable is the margin by which the old record was broken—spring 2012 temperatures were a full 1° F above the previous most extreme season, the winter of 1999 - 2000. All-time seasonal temperature records are very difficult to break, and are usually broken by only a tenth of a degree. To see the old record crushed by a full degree is a stunning and unparalleled event in United States meteorological history.

The Crab Spider catches and kills a honeybee.

U.S. heat over the past 12 months: 
One in half-a-million-years event

The U.S. record for hottest 12-month period fell for the second straight month in May. The June 2011 - May 2012 temperatures smashed the previous record by a startling 0.4° F—a huge margin to break a record for a 1-year period.

The past twelve months have produced America's 2nd warmest summer, 4th warmest winter, and warmest spring on record. Thirty-two states were record warm for the 12-month period, and an additional ten states were top ten warm. Each of the 12 months from June 2011 through May 2012 ranked among the warmest third of their historical distribution for the first time in the 1895-present record. According to NCDC, the odds of this occurring randomly during any particular month are 1 in 531,441. Thus, we should only see one more 12-month period so warm between now and 46,298 AD—assuming the climate is staying the same as during the past 118 years since reliable record keeping began.

The unusual warmth was due, in part, to a La Niña event in the Pacific that altered jet stream patterns, keeping the polar jet stream much farther to the north than the climatological normal. However, it is highly unlikely that the extremity of the heat during the past 12 months could have occurred without a warming climate. 

A Green Bee (Genus Agapostemon) or Metallic Green Bees on a flower.

Second warmest May, warmest year-to-date period on record

May 2012 was the second warmest May in the contiguous U.S. since record keeping began in 1895. Twenty-six states had a top-ten warmest May, and no states had a top-ten coolest May. The January - May 2012 period was the warmest January - May period since record keeping began in 1895, with temperatures 5° F above the 20th century average for the period. This broke the previous record set in 2000 by an unusually large margin—1.3° F. 

A Tiger Beetle (genus Cicindela or Tetracha) killing an ant.

Tiger Beetles often have large bulging eyes, long slender legs and large curved mandibles.
Most genera of Tiger Beetle are solid black while Cicindela and Tetracha are often brightly
colored, like this specimen.

Most extreme spring and January - May period on record

NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, was 44% during the spring March - April - May period. This is more than twice the average value, and spring 2012 was the most extreme season of any kind in U.S. history. A list of the top five most extreme seasons since 1910, as computed using the CEI, show that two of the three most extreme seasons in U.S. history occurred in the past 12 months:

Spring 2012: 44% Winter 1979: 42% Summer 2011: 39% Fall 1985: 39% Spring 1934: 38%

Tiger Beetles are remarkably fast and are known for their aggressive predatory habits.

Remarkably, 81% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during spring 2012, and 71% of the U.S. of the U.S. had warm minimum temperatures in the top 10%. The percentage area of the U.S. experiencing top-10% drought conditions during spring was 18%, which was the 19th greatest since 1910. Extremes in 1-day spring heavy precipitation events were the 8th largest on record. The year-to-date January - May period was also the most extreme such period in U.S. history, with a CEI of 43%. 

The Tiger Beetle finishes off the unlucky ant.

Climate change theory predicts that, in general, the climate should warm, wet areas should get wetter, and dry areas should get drier. The spring 2012 Climate Extremes Index reflects this pattern.