When selecting a planting location for a Salvia that prefers full sunlight, you probably need a spot that receives more than six hours of sunlight daily. Many Salvias are happy with as much sunlight as they can get.
However, local conditions may make it preferable to give a full-sun species a bit of shade daily. These include high altitude settings as well as a severe lack of rainfall during hot weather.
At high altitudes, the atmosphere is thinner and does less to moderate sunshine, which means that daytime temperatures can become extreme. If sufficient, moisture can help plants surmount this heat. In dry, high-altitude areas, it may be best to plant your full-sunshine Salvias in a part of the yard offering some shade during the afternoon, which is the time of day when sunshine is most intense.