When coupled with the large proportion of land-based official recording stations which are near or inside the heat-sink islands that are cities and airports, a whole bunch of areal averaged temperatures make the entire countryside between those stations look to be at the same temperatures of the two averaged heat-sink islands defining the extremes of that “recorded” area.
This is affirmed by satellite temperature monitoring, which shows decadal decreases in net world heat (including ocean temperatures).
Note that this year, only NOAA started using these poor ocean heat over-recorders in their averages as legitimate temperature sources. The rest of the world so far refuses to jump on to including these, due to their obvious, known, fake inflation of temperature.
They do the same thing with land based reading too. Find a station warmer then the others and then adjust the others up. It is really criminal how NOAA tortures the data to get the desired outcome.