For the Lower 48 States of the U.S., May Was the Wettest of 1,452 Months on Record

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By Tom Yulsman
Jun 9, 2015 8:27 AMNov 20, 2019 2:36 AM


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Most of us probably know that May was astonishingly wet in much of the country. But now, thanks to a report just released by the National Centers for Environmental Information (formerly the National Climatic Data Center), we know just profoundly soggy it was. For the contiguous states, not only was it the wettest May on record, but in 121-years of record-keeping it was also the wettest month ever. To put it another way, this past May was wetter than all 1,451 months preceding it. All that cloudiness and moisture helped hold temperatures down during the month. The average temperature for the contiguous United States was near the median value for the 121-year record. But there were exceptions to this moderate picture — most dramatically in Alaska, which experienced its warmest May, with an average temperature that was a shocking 7.1 degrees F above the long-term average. Also, as moderate as the U.S. average temperature might have been in May, the weather overall has been anything but. According to the report, the U.S. Climate Extremes Index for the year to date has been 30 percent above average, with the contiguous United States experiencing its 19th highest value on record. This was largely due to extremes in warm maximum and minimum temperatures, as well as the number of days with precipitation.

An animation of images centered on Colorado from NASA's Terra satellite, one from June 8, 2013 and the other acquired June 8, 2015. (Source: NASA) For Colorado, where I live, May's moisture has been in stark contrast to where we were at this time just two years ago. In early June 2013, severe to exceptional drought gripped 72 percent of the state. The worst of it was in the southeastern corner of the state. Today, a little less than 17 percent of the state is in drought, and only a small sliver of the southeastern portion is abnormally dry. I created the animation above to illustrate the difference. The first image in the animation was acquired by NASA's Terra satellite on June 9, 2013, and the second today (June 8, 2015). Notice how much greener things are now on the plains east of the mountains. I'm not complaining.

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