Gen 41:
28 “It is just as I said to Pharaoh: God has shown Pharaoh what he is about to do. 29 Seven years of great abundance are coming throughout the land of Egypt, 30 but seven years of famine will follow them. Then all the abundance in Egypt will be forgotten, and the famine will ravage the land. 31 The abundance in the land will not be remembered, because the famine that follows it will be so severe. 32 The reason the dream was given to Pharaoh in two forms is that the matter has been firmly decided by God, and God will do it soon.
The drought of the time of Joseph was during the Middle Kingdom period, the beginning of which is divided from the end of the Old Kingdom by the first intermediate period (which was a chaotic, disunited mess).
http://egyptphoto.ncf.ca/amenemhet%20III%20hawara5.htm