In order to find the place with the highest or lowest temperature ever recorded in a country,
as many as possible measuring stations are required, as well as long and equal measuring
periods and constant measuring conditions.
Usually these conditions are not fulfilled. The values are based on different lengths and periods of measurement time series.
Stations were relocated or the environmental conditions near the
station changed. Stations that were formerly located on the outskirts of a city and surrounded by
fields or meadows now may be surrounded by densely populated and industrial areas.
The specific location of the station also plays an important role: location on a slope, location on a hill or in a
valley. Extremely low temperatures can occur even in
small terrain depressions, and are representative only for the immediate
surroundings of the station. At the same time, a nearby town on whose district the station is located may experience
completely different temperature conditions.
It is immediately obvious that wind measuring conditions at
different locations are hardly comparable.
Wind measuring within cities is subject to the specific flow conditions
caused by buildings. Similarly, topographical conditions (valleys, mountains)
have very different effects on wind direction and speed.
Usually the wind is measured at 10 meters above ground - even
this requirement can not be met at all stations.
The measuring principle should also be uniform: The wind peak value at
the Zugspitze was obtained by a dynamic air speed indicator
that was oriented parallel to the slope inclination.
This measurement principle is otherwise not applicable.
Astronomically, the maximum annual sunshine duration is
exactly half a year (approx. 4383 h) in every place on earth.
When measuring the sunshine duration, there should be no shading effects by buildings or trees.
In low sun, however, a temporary shading in most places can rarely be avoided.
The situation of the station is even more serious when it is in a (narrow) mountain or alpine valley.