Hypernym for "interpolation" and "extrapolation"

"data fitting" or "curve fitting" - depending on the context.

Estimation is defined at Wikipedia thus:

Estimation is the process of finding an estimate, or approximation, which is a value that is usable for some purpose even if input data may be incomplete, uncertain, or unstable. The value is nonetheless usable because it is derived from the best information available.

It was my first choice for an answer because it is used in science and engineering.

My second choice was Approximation but after reading the Wikipedia section it seems to focus on the use of a simpler model as a substitute for a more complex model. I believe that amounts to the same thing as estimation.

Now, under the heading Numerical analysis, Wikipedia states

The field of numerical analysis includes many sub-disciplines. Some of the major ones are ... Interpolation, extrapolation, and regression

So perhaps numerical analysis is the best hypernym, even though it doesn't "sound" much like interpolation and extrapolation. On the other hand both estimation and approximation do "sound" right, both as headings or as actions.

In either case, you're approximating the temperature, and are thus performing an approximation.