For the people who live in Jeddah, so if they resolve to perform `Umrah from where they stay in Jeddah, then they have to enter Ihram from Jeddah, because Jeddah is closer to Makkah and is closer than the miqat. The Prophet (peace and blessings be upon him) said, after mentioning the miqats (the appointed stations to assume ihram): “Whoever is closer than that should enter ihram from his home and the people of Makkah should enter ihram from there.” (Al-Bukhaari).
Thus, Jeddah is the miqat for its people and for those who live there.