Definition "Outside temperature" - average over several days?

In the configuration of the heating system, the term Außentemperatur repeatedly appears. It can hardly mean the current temperature, which fluctuates daily depending on the weather, but rather an average over several days, right?

Can someone explain to me how the "Außentemperatur" is calculated?

Depends on the heating. And then also on the value. With Vaillant, for example, it can be the currently measured outside temperature or the 24h average. ;-)

And to make matters even more complicated, most heating systems now also offer the option to take the weather forecast into account ;)

With Nibe, the default is the average over 24 hours.

Do you mean the heating system planning, i.e. the [Normaußentemperatur]? The [Normaußentemperatur] is the lowest temperature of a cold period, which must have occurred 10 times within 20 years over a period of at least two consecutive days.

Or the temperature in the heating system (which you already have). There you have to distinguish whether it is the outside temperature at which the heating turns on (summer shutdown as a possible term) or the outside temperature for the current control.

So it can be, as others have already written, an average or something similar or the actual outside temperature. It is not always that simple.