Chuck Wiese linked to a chart he said was compiled by Mark Albright, showing Salem's annual mean daily maximum temperature, 1932-2013. But he couldn't provide the underlying data, or explain why the chart ends in 2013.
The National Weather Service gives monthly temperatures for Salem from 1892-present -- Tmax, Tmin, Precipitation and Snow. Some data are missing, with an "M" for that month. I only took an annual average only if there were no missing months. Here's what I get for Tmax (all temperatures in Fahrenheit):
I don't know where Albright or Wiese got their data, but the data I obtained shows a trend in Tmax of +0.15°F/decade.
Wiese explained why Albright began his plot in 1938:
Mark Albright chose 1938 as a starting point because before this time, Salem, OR was not a first order station. The conversion took place in 1937 and before this time, there were months of records missing from the station.Starting at 1938, my data show a linear trend of +0.09°F/decade.
By the way, the trend of Tmax since 1970 is +0.31°F/decade.
I do find the trend from 1938-2013 to be zero. These last four years were very warm here, and make a significant difference.
PS: To be clear, I'm not faulting Mark Albright. He made a graph and it stands on its own. I'm calling out Chuck Wiese for trying to push data that aren't up-to-date.