1- Is there a temporary mahram? 2- What is the ruling on a man shaking hands with a non-mahram woman?

Temporary prohibitions may include the prohibition of marrying two sisters simultaneously, which is forbidden by consensus, based on the Almighty's saying: "and that you take in marriage two sisters together". It is also forbidden to marry a woman alongside her maternal aunt or paternal aunt. Moreover, a man who has four wives is not permitted to marry another until he divorces one of them. Shaking hands with non-mahram (definition) women, such as a paternal uncle's daughter or a paternal aunt, is forbidden based on the Prophet's (PBUH) saying: "For one of you to be stabbed in the head with an iron needle is better for him than that he should touch a woman who is not lawful for him." Shaking hands is only permissible with a woman who is a permanent mahram. However, a temporary mahram, such as a sister's husband, is not allowed to shake hands or be in seclusion with her.