Germany is a little larger than Missouri and Arkansas combined, and has a fairly coherent long term temperature record at 13 stations.
There has been a warming trend in Germany since 1980.
This can’t be explained by UHI, HOHENPEISSENBERG is a rural station at 3,100 feet elevation, and MUENCHEN is an urban station at 1,700 feet elevation.
Munich is warmer, but the two stations track each other very closely.
These two stations have warmed considerably since 1980, and I don’t see any reason to think the trend isn’t real.