The water temperature depends on the type of tea. Black teas and tisanes should be brewed at 210°F, green and yellow teas – at 160-180°F, white teas – at about 200°F, oolong teas – at about 190°F, dark teas – at about 203°F.
There are some kinds of teas that might require different water temperature. For example, first and second flush Darjeeling teas and high elevation Ceylon teas have lower oxidization and therefore should be steeped like oolong teas at 190°F to prevent bitterness.