So far this month, we’ve only touched 90 degrees once in D.C. – on June 4. Unless we touch 90 Wednesday (an outside chance), it’s likely we’ll have had only that one 90-degree day through June 15. Over the past 14 years, a lack of 90+ days in the first half of June has often portended a summer that’s not abnormally hot.
Ranking early June 90s
When ranking the 2000s in terms of how many 90-degree days logged in the first half of June, we see that the highest counts tend to equate to the hotter summers (2 degrees hotter than normal or more qualifies as “hot” in the ranking table).
But there are definitely exceptions. For example, in 2000, there were 4 90+ days in the first half of June, and it ended up being a cool summer. The summers of 2006 and 2007 only saw one 90+ day in early June, but closed warmer-than-normal.
I find it interesting that 2014 is grouped near 2009 and 2004, both years with developing El Niño summer patterns like forecast this year (that also evolved similarly in the north Pacific ocean in terms of atmospheric response).
Odds summer will be cooler than normal?
Only five of the past fourteen years (nearly 1 in 3) have verified on the cool side of normal, so the probabilities of a cool summer overall are probably low. But, given that the higher hot summer incidence tends to see more 90-degree days in the first half of June, the odds may be closer to 50% rather than the standard 33% from looking at all the data. Whatever the case, the lack of 90s in the first half of June is a welcome respite from the very hot 2010-2012 series of summers we experienced.