i normally try to have 80-90 but im sure it can fluctuate personaly i have done it in 70-75 beffore but not with 100% success i normaly do it in a bottle of water ontop of my power pack or in the kitchen
and if you are using tap water let it sit for atleast a day so all the chlorine and other shit can evaporate and so it reaches room temp (but again i have done it with out letting it sit and used cold water...)