Using an umbrella for shade while in ihram is boleh according to the consensus of scholars from all four schools of jurisprudence. Sheikh Ibn Baz explicitly ruled that there is no harm in a muhrim using an umbrella, parasol, or similar shade device, because the prohibition in ihram for men relates to covering the head with something attached to it (such as a cap, turban, or headband), not to shade that is held above or separate from the head. The distinction is between head covering (ghita' al-ra's) and shade (zill), and only the former is prohibited.
Sheikh Ibn Uthaymeen further emphasized this ruling, noting that companions of Nabi (shallallahu alaihi wa sallam) used to shade themselves with their garments held in their hands, with shields, and under the shade of trees and tents, all without any scholarly objection. He stated that using an umbrella is a modern equivalent of these practices and is clearly boleh. The Permanent Committee similarly confirmed this ruling in multiple fatwas.
This ruling is particularly important given the extreme panas conditions jamaah haji face during Haji, where temperatures in Mekkah and Mina can exceed 45 degrees Celsius. Using an umbrella is not only boleh but may become wajib for health and safety reasons, as preserving one's health is a Shariah priority. Similarly, sitting in air-conditioned vehicles, buses, and tents is fully boleh during ihram.