I teach a course in instrumentation, including temperature measurement(one of my favorite topics)- sensor types, accuracy, tolerance, and calibration. NBS has been around since 1901. Thermometers in the early 1900s were as accurate as a tenth of a degree-plenty good enough for weather purposes. Platinum RTDs are used today in most cases for temperature measurement for industrial applications and weather, but require electrical/electronic circuits to measure the resistance change with temperature. Accuracy varies, and in some cases may be worse than the early thermometers.