Is it permitted to open an umbrella on Shabbat?

Hello,

The reason it is forbidden to open an umbrella on Shabbat is because there is a prohibition against creating even a temporary shelter on Shabbat. Additionally, even if the umbrella were closed before Shabbat, it is still forbidden to use it on Shabbat—see sources.

Sources: In the responsa of Makhtem LeDavid (Orach Chaim 1), it is stated that even if the umbrella was open before Shabbat, it is forbidden to carry it on Shabbat, because by carrying it he is creating a shelter, which is included in the prohibition of making a temporary shelter on Shabbat. See there.

Moreover, in the responsa of Noda B'Yehuda (part II, end of section 30), there is a doubt whether there is a prohibition on creating a shelter if the umbrella was open before Shabbat, but he also agreed that there is certainly a prohibition in terms of uproar, as someone who sees him carrying an umbrella on Shabbat may suspect that he opened it during Shabbat. And according to all opinions, the prohibition of uproar applies even in a public scenario. See there.

Similarly, the Birchay Yosef ruled against opening an umbrella in Orach Chaim (Beit Shiyurim 308) citing the responsa of Givat Pinchas, as authorized by the renowned Rabbi Pinchas Aniyah z"l, and the Pitech HaDvir (ibid., letter g) and the Ben Ish Chai (year 2, Parashat Shemot, letter 8). Additionally, see the Biur Halacha (section 308, paragraph 8, DH Tefach). Furthermore, it was concluded in the responsa of Yechaveh Da'at (part II, section 43) and in the book Hilchot Olam (part IV, pages 3-5) and in the book Chazon Ovadia Shabbat (part V, page 357).

Wishing you much success,

Hillel Meirs