Theoretically no, the database we used contains weather station data from all over the world. However during our analysis we found that the quality of data from international stations was a lot more varied - as measured by many factors such as geographical distribution of stations, regularity of measurements and number of implausible outliers. I would still like to come back to this eventually & try to iron out as many of those issues as possible - but for the scope of this project it was much easier to just use US data as it is extremely well-curated.