Record Warmest 12 Months in U.S.;Odds of Occurrence Less than 2 in Million

As previously reported here, only 4 weeks out of the last 52 ending in May were colder than average in the U.S. The National Climatic Data Center (NCDC) has now reported that the 12 months from June 2011-May 2012 were the record warmest of any 12-month period in U.S. climate history, surpassing by a wide margin the year ending in April. Three of the top 5 warmest 12-month intervals have now ended in each of the last 3 months.

The NCDC further reports that "each of the 12 months ranked among the warmest third of their historical distribution for the first time in the 1895-present record. The odds of this occurring randomly is 1 in 531,441."

NOAA/NCDC Confirms U.S. Spring Temperatures Smashed Heat Record by Unprecedented Amount; Largest Margin of Any Season on Record

NOAA's National Climatic Data Center (NCDC) late this morning confirmed that spring 2012 (March-May) temperatures crushed the seasonal heat record, as preliminary CapitalClimate analysis had previously indicated. The final average of 57.1° was equal to the average of earlier estimates and was the largest departure from the long-term average of any season on record since national data began in 1895.

As the map shows, every state east of the Rockies had a top-3 warmest spring, and 31 of those, from New England to the Northern Plains and from the Great Lakes to the Gulf Coast, had an all-time warm record.

From the NCDC report:

The national temperature of 57.1 degrees F during spring was 5.2 degrees F above the long-term average, besting the previous warmest spring of 1910 by 2.0 degrees F. This marked the largest temperature departure from average of any season on record for the contiguous United States. The spring of 2012 was the culmination of the warmest March, third warmest April, and second warmest May. This marks the first time that all three months during the spring season ranked among the ten warmest, since records began in 1895.

Record and near-record warmth dominated the eastern two-thirds of the nation during spring. Thirty-one states were record warm for the season, and 11 additional states had spring temperatures ranking among their ten warmest. Only Oregon and Washington had spring temperatures near their average.

U.S. Average Temperature Warmer Than Climatology All But 4 Weeks in Past Year

U.S. weekly average temperatures compiled by the National Climatic Data Center from National Weather Service reports show that there have been only 4 weeks in the past year that have not been warmer than the climatological normal. None of these has been in 2012, although the past week, ending June 2, was close, at +0.28°F. The most recent cold week ended on December 10. The only 2 consecutive cold weeks were in November. The preliminary national average temperature of 55.22° for the past year was 2.23°F warmer than climatology.

U.S. Record Warm Spring Caps Record December-May

Following a near-record warm winter, the record warm spring by a wide margin in the U.S. has produced a record warm 6 months of December-May. Preliminary May figures combined with the National Climatic Data Center reports for the previous 5 months yield an estimated average of 48.1°, over 1°F above the old record of 46.9° in 2006. Seven of the top 8 warmest winter-spring periods have now occurred in the last 14 years beginning in 1999.


The charts to the right (click to enlarge), from the NOAA Earth System Research Laboratory, show the December 2011 to May 2012 average temperature departure from the 1981-2010 climatology and the difference between the 2011-12 average and the corresponding months for 2005-06.

Preliminary Data Continue Supporting US Record Warm Spring Estimate

June 7, PM Update: See update for official report from NOAA/NCDC.

June 5, PM Update: Preliminary National Climatic Data Center analysis, based on National Weather Service data, shows an average May temperature departure from normal of only 2.33°F. This would reduce the U.S. spring average about 0.7° from the earlier estimate. However, the adjusted average would still exceed the old record by a wide margin:



June 4, PM Update: Using a larger subset of 237 National Weather Service stations for May 1-31, the average is 3.5°F above the 1981-2012 climatology, so it's very likely that the May average was within 0.1°C of being 2°C above climatology.

Original post:
Now that preliminary data are available through the end of May, earlier estimates of U.S. record warm spring temperatures are being further confirmed. For the meteorological spring months of March through May, temperatures averaged above climatology in nearly the entire country, except for the immediate Pacific Coast:
Much of the Midwest was 3.5°C or more above average, with most or all of 5 states above 4°C.

Looking at the averages from 215 official National Weather Service reporting stations for the weeks ending from May 6 through June 3, the U.S. May temperature would average 3.7°F above the 1981-2010 climatological baseline:


This puts the May 2012 national average temperature at 65.5°, which edges out the record warmest May of 1934 by 0.1°.

Combined with the significantly above-average temperatures of March and April, it's very likely that the final spring temperature will exceed the previous warmest spring of 1910 by as much as 2.4°F. Five of the top 8 warmest springs will now have occurred in the 13 years of this century.


Official U.S. temperature averages will be published by the NOAA National Climatic Data Center in about a week.

Kim Martucci Pregnant (And Back to Our Regular Programming)

Since celebritology is MUCH more important than the fact that the entire continental U.S. has just smashed the record for warmest spring in history by an incredible margin:

Yes, Kim Martucci, weekend substitute weathercaster on WRC-TV (Channel 4) confirms that she is again pregnant, this time with her second child (and looking somewhat less red-headed on tonight's hockey-delayed broadcast).

Yes I am! MT @PLMuse Are you #expecting? If so, expect these common problems during your pregnancy! bit.ly/JkHpYo #pregnancy

— Kim_Martucci (@WeatherKim) May 15, 2012

Fat Lady Preparing to Sing: U.S. Crushing Warmest Spring Record

May 30, 9 PM Update: As a check on the temperature estimate methodology described in the previous update, the same procedure was applied to a set of 247 stations for the month of April. The result was only 0.1°F different from the official U.S. April average from NCDC.

May 30, 5 PM Update: Preliminary data continue to confirm that the U.S. average spring temperature is likely to smash the old record high by a wide margin. The latest national average map, through May 28 (Monday) shows some cooling creeping into the Pacific Northwest and northern Rockies, compared with the month-to-date 4 days earlier (in original post below). However, the warmth has intensified from the Midwest eastward to the Atlantic coast, with maximum values exceeding 3.5°C above normal in central Kansas:

In order to estimate a numerical value for the national average May temperature departure, CapitalClimate compiled the weekly average temperature departures from normal for the 4 weeks ending May 27 at 215 major National Weather Service weather reporting locations across the 48 contiguous states. The final figures from the National Climatic Data Center (NCDC) will include many more stations and adjust for geographical distribution, but the estimate indicates a 4-week average of 4°F above normal. Even with somewhat cooler temperatures for the last 4 days of the month, it appears that the final spring average will come in at the high end of the range of estimates in the original post (near the "2012+2C" figure of 57.4°).



Original post:
As suggested last week, the U.S. is well on its way to crush the record for warmest spring since national temperature data began in 1895. Here's an indication of just how far that record could go. The previous record spring in 1910 had a national average temperature of 55.1°. However, the March 2012 temperature exceeded March 1910 by 0.5° to set a new record for the month. April 2012 then exceeded April 1910 by 1° (see the charts to the right).

At this point, May 2012 would have to be 1.5° cooler than May 1910 to avoid exceeding the record. What are the chances of that? Somewhere between slim and none. Here is the temperature departure from average for May 1-24:

Note that the chart is in °C. Nearly all of the country is above average, with large areas over 2°C higher. How did May 1910 compare?


Most of the country was below average. In fact, May 1910 was 1.8°F below the 1981-2010 average overall.

If the last 7 days of the month completely reversed the May 1-24 pattern shown above so that May averaged equal to the climatological mean, Spring 2012 would still be 1.1° warmer than the old record, as big a margin as the difference between the current record and the 10th place year of 1977. If May averages as much as 2°C above climatology, which looks quite plausible, the spring average would be an eye-popping 2.3°F above the old record (see the chart at the top of the post).

Meanwhile, daily high temperature records, while not at the incredible March rate, continue to outpace low records by a huge ratio (click to enlarge):