May 2017 Most Extreme U.S. Temperatures

With summer heat in full swing I have been blogging away on other issues, but I have not forgotten about our monthly extreme temperature record awards.ūüėä In previous posts on this site and on Weather Underground I introduced the weather and climate world to the concept of an Extreme Temperature Index. Once more lets apply the current index algorithm to reports from May 2017 in the National Center for Environmental Information‚Äôs surface records site¬†and see what the most extreme event and location was. Keep in mind that these are not the hottest and coldest records, but the records that differed farthest from the norm, climatologically. Drop me a note if you think you have spied a more extreme record and its location than what is presented here for May. The posts I am referring to are:



The current Extreme Temperature Index is defined by:


In the ETI equation the difference between the old and new record is the most predominant factor,  so I have selected a record low minimum and record high maximum with the highest T sub r.

The big cold winner was Upper San Juan, CO, which broke their old record low minimum by 14 degrees on May 19th. Hundreds of record lows were set via a strong late season winter storm in mid-May in the Rockies and western high Plains. I took the norms, or average high and low for the date the new record was set, for May 19th, from the closest large major city, Durango, Colorado:


The big hot winner was West Rockport, ME, which broke its record high by 13 degrees also on May 19th. The atmosphere across the contiguous U.S. was running in extreme mode in mid May. Clinton, LA did have a more extreme record, but I suspect that the tally there was faulty. A strong upper ridge of high pressure had built well east of the winter storm over the East leading to a mini heat wave. I plugged in the average max and min for Augusta, ME, the largest major city closest to Rockport into the ETI equation:

Just like in April the most extreme hot record was greater than the low record. This time around the difference between the average max and min temperatures in the denominator if the ETI equation was the most important factor since San Juan, CO has a much more continental climate than  Rockport, ME. ETI values will be lower the higher the spread between the average max and min.


Please drop me a line if you have better candidates for the most extreme temperature records for May 2017.

The Climate Guy

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