I want to obtain the quantity of precipitation for each municipality in Brazil on a given year. For that, I'm trying to use IDW interpolation on QGIS to interpolate the precipitation data from weather stations to municipality centroids. I have two shapefiles, one for the weather stations (with station long-lat and total precipitation data) and another with municipality polygons (from which I obtain the centroids). I'm new to QGIS, but I'm already able to perform an IDW interpolation for the entire map, but cannot find a way designate specific values to the centroids.
If that is possible on QGIS, how do I do it?