If the boiling point of water is at 100 °C, why does a hydrate need to be heated higher than that to evaporate water from the crystals? Does it have anything to do with their intermolecular forces?
Hydrates are substances that have absorbed water into their crystal structure. Much of this attraction is caused by interparticle forces (notice I didn't say 'intermolecular'). Since water has a very strong dipole, it is quite often attracted to not only other molecules, but ions inside ionic crystals.
In some cases, water can easily be attracted into the crystal structure so much that it makes the substance deliquescent. Other times, crystals may only absorb some water, nor others. This is because of the competition in attractions between an ionic crystals ion-ion attractions (ionic bond) and the ion-dipole attractions to water (interparticle force).
To finally discuss why we have to go above the boiling point of water $100^\circ C$: If the attraction between the dipoles of water and ions of the salt are stronger than the standard interparticle forces of water, it will take more energy to break those forces and transition them to gaseous state.
Likewise, if a substance has quite weak ion-dipole forces, it would more readily release the water and dehydrate without much or no added heat.