Weather and biology are extremely complex systems; but ones in which we do have an understanding of the physical forces involved, and the difficulty of making predictions. There is very little actual subjective interpretation involved (moreso in medicine than in meteorology, which is a branch of physics), only mathematical uncertainties and limits to our ability to observe and model. Meteorology involves a highly chaotic system, and chaotic systems have limits to the predictive capabilities that can be derived from them. But we can still understand and quantify where those limits are, and estimate probabilities; and as the technology available to observe and model these systems improves, so does our ability to understand them and make predictions about them. Medicine in particular is still a very young science, and we are making great strides in understanding the complexities involved and enhancing our predictive capabilities.
Social sciences lack that predictive value; because they are not as amenable to mathematical description or statistical analysis. There has been, so far, no predictive value to any of them that exceeds chance by any significant degree. They are strictly observational. The fields are rife with subjective interpretation and agenda-oriented approaches. One could (and some have) make the argument that that is due to the tremendous complexity involved; and that time will provide us the tools to introduce objective measurements with predictive capacity. That may be true; and should it become so, then they could be treated as any other physical science. But that day is still far off, if it ever comes; particularly since there is still no real consensus on exactly what we can measure, and how.