Between the ranges of 41F and 120+F, the traditional mercury bulb thermometer remains extremely accurate when read by a competent observer; the modern machines are designed to be self-calibrating and there word is gospel.
The WBAN manual lists the requirements for the location, design and construction of a classic instrument shelter in the (then) interests of uniform measuring procedures; since the advent and adoption of the automated units all that is largely ignored.
there-their, sorry.
“when read by a competent observer;”
I don’t doubt this to be true, was the training done after a full day of riding horses and trying to find food and water to eat?
It is interesting to note that "Average temperature" will change consideraby based upon whether the daily low and daily high are averaged together, hourly readings are taken, and what time of day the readings are taken. These have all changed considerably over the last few years.
I've seen some initial tests suggesting a large difference in temperature readings between the testing stations painted with whitewash, and painted with white latex paint. This in addition to the stations that sit adjacent to parking lots that weren't there a decade before.