GrowCNanswered grow question 4y ago I let temperature during lights off to drop to 70f (21c). With lights on I want a maximum of 85f (29.5c). During flower I try to keep the relative humidity at 50% but it can sometimes be difficult to keep it below 60% and has caused no problems. Just make sure you have good airflow in the tent to help prevent bud rot if your humidity runs high.