Not only was it the hottest June on record, the month before that was the hottest May on record. Things are just hot in general.

The National Oceanic and Atmospheric Administration announced Monday that last month's average global temperature was 61.2 degrees, which is 1.3 degrees higher than the 20th century average. It beat 2010's old record by one-twentieth of a degree.
...
And that's only part of it. The world's oceans not only broke a monthly heat record at 62.7 degrees, but it was the hottest the oceans have been on record no matter what the month, Arndt said.

But, hey, remember when it snowed a couple years ago? So much for global warming!