The 7 lipos I lost to storage at 50% were inside the house under AC and never saw temps more than 80F. I store mine at room temp.
With the wide varietry in quality of cells out there, not sure a universal guide is possible. My higher quality lipos (Flightpower, NeuEnergy) behave diff than the less expensive ones (ProTek, Integy, DualSky, Nexus, Vampower, etc).