Temporary marriages are on the increase among the youth, especially students at university.

Answer

The type of temporary 'marriage' you mention is not permissible. They live in zina. Temporary 'marriage' is a Shiah practice. It is legalized adultery. The girls are not innocent and the parents are not innocent. The girls are just as guilty and corrupt as the boys. Allah Ta'ala has ordained the punishment of zina for both the boy and the girl. The assumed 'innocence' of the girl will not allow her to escape flogging. All parties involved in this type of fornication are scoundrels. The parents are the worst scoundrels and villains. They are the first cause for plunging their daughters into fornication by allowing them to make contact with males who are haraam for them. They are the destroyers of their children by allowing them to plunge into the cauldron of vice and immorality, namely, university. What can be expected from the immoral male-female contact, especially in these evil educational institutions? In fact, secular educational institutions are akin to brothels.