A meteorologist friend came across this CPC section on seasonal and annual trends.  He quickly noted that they chose a date to start the trend that showed the maximum possible trend results.

See full image here

You will notice that the trends are for the period from 1976 to 2005. They start at the time of the Great Pacific Climate Shift to the PDO warm mode in 1976-77. Had they done the trend over the whole period of record back in the warm peak in the 1930s, they would have seen little trend (0.18F versus 1F for the 1976 to 2005 period). Max to max and min to min changes provide the real trends in cyclical patterns.

See full image here

The 1930s was when most of the all-time heat records were set for the United States.

See full image here Read more here.