I recall a few years ago that Phoenix was the subject of hysterical news—Phoenix, known to be the hottest city in North America, had a July that was even hotter than usual. Their weather station is situated on the grounds of Sky Harbor Airport, which is also well within the Phoenix heat island, which has grown tremendously in size the last thirty years, by which comparisons were made. Of course the heat dome moved on in due course, and nobody has seen or heard about it since. But the media had their story for awhile.
If there is always a pick-&-choose where the heat or cold is tested, then there is little way of knowing whether or not the earth is heating or cooling as a whole.