I am looking for some kind of software (free software) that allows me to make an interpolation like PRISM software.
The interpolation used in PRISM is a
local regression and accounts for spatially varying elevation relationships; also accounts for effectiveness of terrain as barriers, terrain-induced climate transitions, cold air drainage and inversions, and coastal effects
What I am aiming to interpolate are climate time-series datasets.
Best Answer
Given you've tagged R in your question I'd take a look at the CRAN Spatial View and the gstat package in particular. Not sure if it has the exact PRISM interpolation method, but it would certainly be a good place to start.
Alternately you could look into the SciPy interpolation and ndimage subpackages if you'd prefer to work in Python.