June recap: volatile temperatures with a hot finale

July 10, 2012

The high level of extremes seen this past month is hidden in the less-than-exciting mean data. The month that delivered our hottest June peak temperature on record (104F last Friday) only came in as the 23rd warmest on record. It was the coolest June since 2009 and the wettest since that month too. But it still finished drier than normal.


Examining the distribution of temperatures during June, we spent more days with highs in the 80s than any other high temperature range, but the 90s were close behind:


And who can forget the historic derecho (thunderstorm) event of June 29? In addition to the widespread, destructive 60-80 mph winds, it produced a quick 0.58” of rain at Reagan National, about 25 percent of the month’s rain output.

From a big picture pattern standpoint, the atmosphere in the Northern Hemisphere is going through a transition process between the outgoing La Niña pattern that has dominated the last two years’ weather and a new incoming El Niño regime. This probably contributed to the higher degree of volatility, but clearly the hotter influences from the departing Niña won the month.

It is interesting to note that through June, the developing El Niño is one of the slowest on record. We are seeing signs that the evolution is finally picking up speed, which may lead to a wetter/cooler pattern shift later this summer- but it may not happen fast enough for July. After close to average temperatures this week, hot air may return next week.

Related link: What is Washington, D.C.’s weather like in June? Breaking down norms and extremes

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