Just did a quick Google search and it looks like 55 is the ideal storage temp (45 to 65 range). We picked up a small one at one time, thought we could keep water cold, but like you've found, not very cold. Put it at the curb with a Free sign and gone quickly.
Michelle & Ann
2018 Chevy 3500HD Crew Cab High Country DRW, D/A, 2016 RW39MB, Dual ACs, Auto Level, Auto Sat Dish, Stack W/D, King Sleep #, 17.5" Sailuns w/Disc, MORryde IS & Pin, Comfort Ride Hitch, 5.5 Onan, Res Fridge & Induction Cook Top