According to the NOAA, the warmest June in USA history was 1933.

Followed by 1918, 1994, 1988, 2002, 2006, 1952, 2010, 1931, 1934, 1911, 1936 and then in 14th place: 2012.

Even with the NOAA cooling the past, the 1930s were hot.

 

 

 http://www.ncdc.noaa.gov/oa/climate/research/cag3/na.html