If a person is severely dehydrated, their extracellular fluids will become hypertonic to the intracellular fluid. what do you predict will happen to the person's cells

In hypertonic condition, osmosis will occur. In this case, the fluid will be attracted into the hypertonic solution since it osmotic pressure is higher. This condition can cause the nearby cells losing their water molecule and become shrink.
If it happens for a long time, the concentration of molecule inside the cell will increase since the water is decreased. This will cause the cell undergo lysis.

Droughts cause very arid places such as a desert