Plant your Queen of the Night cereus plant outside in USDA zones 10 and higher. If you live in another USDA zone, pot your Queen of the Night and grow it inside to protect it from frost.
Take your Queen of the Night outside for a little sun only when the outdoor temperatures are higher than 50 degrees F.
Keep an eye on the weather reports. Frost likes to surprise plants by appearing early in the morning and late in the evening. You should really only plant your Queen of the Night outside if you live in an area that does not experience frost at all -- or very little.