Final answer:
Hard meringues are baked at 200°F (95°C), which allows them to dry out and become crisp without turning brown.
Step-by-step explanation:
Hard meringues are baked at a very low temperature because they are essentially being dried out rather than cooked in the traditional sense. For perfect hard meringues, the oven should be preheated to 200°F (95°C), which is just a smidge higher than the boiling point of water. This low temperature allows the meringue to dry out slowly and become crisp without browning or caramelizing, which would occur at higher temperatures such as those used to bake a cake at 350°F or to roast a chicken at 400°F. Baking at a temperature higher than 200°F would be unreasonably large for meringues and could result in an unpleasant texture and color.