How is it possible for a region to receive so much rain (nearly one third its annual total of precipitation in four weeks) yet run out of water four months later.
Since you have placed this in the Social Science section, I will talk about this in terms of social sciences. In particular, I will talk about economics. It depends on the region, of course, but it would not be that much of a surprise for this to happen. This would be particularly true in a poor region of the world.
The simple fact of having a great deal of rain falling at a given time does not guarantee that water will be plentiful for a long time afterwards. Through the hydrologic cycle, the water moves away from the place where it falls. If something is not done to keep the water where it is, it will simply flow away as runoff or sink into the ground and become groundwater. In many poor areas of the world, the infrastructure which would keep the water in place is lacking. If a region is too poor to have dams on its rivers, the water will not be held in reservoirs behind the dams. If it is too poor to have good wells, the groundwater will not be accessible. In terms of getting enough water to fulfill, on a long term basis, the kind of massive demands that modern societies have, the infrastructure for getting water is at least as important as the amount of rain.