Salvia Divinorum lives in the Sierra Mazateca region in southern Mexico and temperatures range from 60-70˚F(16-21˚C) and are ideal. You should keep temperature within the range of 60-80˚F (15-27˚C). Do not let the plant get above 85˚F(29˚C) unless it has been living in a very humid environment (inside a humidity tent). Extra misting during hot days in the summer will compensate for higher temperatures. Do not let the plant get too close to freezing, as it will die if it gets below 32˚F. If you live in a cold climate you will probably will have to take your plant inside during the coldest winter months.
In its native habitat, the relative humidity stays around 100% year round. If you live where it does not stay humid enough(must stay above 50%) you are either going to have to
build a humidity tent or
adapt your plant to lower humidity.
However you decide to grow your plant you should always mist is regularly. It's recommended that you use purified water for misting, but you should be fine using tap water as long as it isn't too hard(nothing above 150 PPM). Ideally you should mist your plant a few times a day, but make sure to do it at least once per day. Depending on how many plants you have you can use a hand spray bottle or a pump-type mister. Another option is to set up a misting system on a timer that sprays for 3-5 minutes several times each day.