A look at weather extremes and the big-picture climate connections.

Hot Summer of 2011 Rewrites Record Books

The summer of 2011 has rewritten the record books. 

Using our record temperature tracker (see below), which draws on the National Climatic Data Center's database, we found that June, July, and August saw more warm temperature records tied or broken than any other summer in the past decade: more than 26,500 record warm temperatures were set across the nation. By comparison, fewer than 3,500 record low temperatures were set — the fewest of any summer in the past decade. These records are daily records — that is, each day’s high and low temperature is compared to the high and lows for that day of the year in the weather station’s history. In addition to the daily records, numerous monthly records were set. In Texas, for example, this summer will go down in history as the warmest summer on record.

A map showing all of the warm and cold temperature records set during June, July, and August across the US. 

Not only that, but NOAA announced today that Texas had the warmest summer for any state in the US going back to when instrument records began in 1895. Oklahoma came in second, with both states beating records set during the infamous "Dust Bowl" era in the 1930s.

Perhaps unsurprisingly, placing this many records on a single Google map made the map run too slowly for most browsers. (Which is why the map on the left is just an image.) Below is an interactive map that breaks the summer down by month. Click on "play" to watch heat waves repeatedly march across the nation.

As is obvious from the swaths of red, the heat was especially relentless in the southern Great Plains, particularly Texas and Oklahoma. In August, more than 4,000 record warm temperatures were set in the Lone Star State alone. (Within each state, hundreds of weather observation stations record hourly data on temperature, rainfall, and other conditions.) That’s almost as many records as are set across the entire nation in a typical month. As Jeff Masters reports for Weather Underground, “The summer of 2011 now holds every major heat record for the city of Austin, including most 100°F days (67 so far), hottest month in recorded history (August, breaking the previous record by a remarkable 2.1°F), hottest summer (by 1.1°F), and hottest day in history (112°F, tied with Sep, 5, 2000).”

Of course, as the climate continues to warm in response to increasing amounts of greenhouse gases in the atmosphere, we expect more record warm temperatures than cold ones. As we reported, record high temperatures in the U.S. are outpacing record lows, which is consistent with what one would expect if temperatures are getting warmer due to global warming.

On average, though, warm temperature records have outnumbered cold records by about two to one. However, this summer the ratio was almost eight to one!

In the future, this summer could look downright cool. According to a study by Climate Central’s Claudia Tebaldi and other researchers, by 2050, record high temperatures could outpace record lows by 20 to one. By the end of the century, the ratio could jump to 100 to one, if greenhouse gas emissions continue unabated. Other research also indicates that many areas may soon shift into a new temperature regime in the next few decades, with much warmer summers featuring intense heat waves becoming the new normal.

« Extreme Planet


By Jim Olson (penobscot Maine 04476)
on September 8th, 2011

Tell the readers why you chose to compare this year with just the last decade.

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By Davidkroodsma
on September 8th, 2011

Hi Jim,

We compared 2011 to the past decade because the National Climate Data Center’s database (which we used for this info-graphic) only provides nighttime low records since 2000.

However, this past decade has been the warmest on record. That means that this summer has been just that much more remarkable.

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By Paul Jepson (97330)
on September 8th, 2011

If you visit the following link http://uspest.org/wea/ and then select “Degree-day maps” followed by “Full USA”, the ‘Deviations from Normals’ map shows a similar pattern, but using longer term data as a comparison and accumulated degree days as the key parameter.

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By Andrew
on September 8th, 2011

Paul - thanks for the link! Personally, I’ve found that the concept of “degree days” is unknown or misunderstood by much of the public, even though this data is very important for many applications. This makes it difficult to base communications products on such data, in my opinion.


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By Paul Jepson (Corvallis, OR 97330)
on September 9th, 2011

You are of course correct about the challenge of communicating climate information with degree day data in a general sense Andrew, but I thought the extent of the differences in degree days from ‘normals’ would be of interest to an expert audience, and secondly I should note that degree day maps make a lot of sense to the farmers that we work with because the equate to plant and pest development. Thanks for the updates, which I have distributed widely to agricultural audiences today. Paul

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By barbara ferguson (Fort White/FL/32038)
on April 9th, 2012

Terrific interactive!  One question?...  When I go to “Play” “June” (or July or August) the year flips every time to 2012, and then I see no way for me to keep the year in 2011…... so of course there is no data yet for June, July and August 2012.  Am I missing something, or is there a bug?  If it is a bug, when you get the bug fixed please let me know and we will share this on our regional water protection (restoration) group facebook page called “Save Our Suwannee, Inc.”.  Thanks for your great work!  SOS facebook page: https://www.facebook.com/pages/Save-Our-Suwannee-Inc/159472370833621 -Barbara

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By Lindsay Harmon
on April 10th, 2012

Barbara - Thanks so much for pointing this out to us! And we’re sorry you weren’t able to quickly get the information you were looking for. The good news is, we just went in and fixed the issue. You’ll notice now there is an option to specify the year, so you can obtain data from any month in any year as far back as 2000, including 2012 so far. Let us know if we can be of any further help!

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