If there is a possibility of rainwater getting diverted towards the soil absorption system you should think of another location, as it may cause the system to become overloaded and fail prematurely.
A septic tank system should never be installed when soil is wet as concrete or other types of septic system installed during wet conditions faces increased possibilities of puddling and soil compaction.
If the water table is high, it will become very difficult to install a septic system in such a place. An engineered system instead of a regular septic tank can be the answer to your problem in such a case.