According to the USHCN thermometers, the three hottest July’s in US history were 1901, 1936 and 1934. But before the data is released to the press, they add almost two degrees on to recent July temperatures relative to temperatures 100 years ago.
NCDC is about to announce that July 2012 was the hottest on record by 0.5 degrees, which means that it was actually about 1.5 degrees cooler than the previous record.
Without the discredited USHCN adjustments, 2012 wouldn’t make the top three.
I think you are misstating the facts. Perhaps the 3 warmest July’s occurred in the 1930’s. But given the very short time period of measured temperatures, it is likely that several hundred or thousand July’s were warmer than the 1930’s.