Don't, 45 is ok, daytime 45 will shoot up to 60 ish at night. So long as there is a small drop in temps at night, this will mean the same space will hold less moisture so your RH will rise. The plant also performs cellular respiration at night. Not so noticable when small, but once in flower the plant creates alot of moisture at night and expels it at night.
Don't guage Rh based off a single metric at a single point at a specific time of day.