My Synology has two drives in it. I just checked and they're reporting ~35 °C (95 °F). It's a relatively warm day today (for the UK), and the NAS is in a cupboard.

OTOH, one of the disks is reporting a SMART error; it's done that since I first put it in the Synology. Earlier versions of DSM tried spinning all the disks up at once -- these disks (Samsung) wanted more power than it could provide -- disk now registers a permanent spin-up failure. I'm just keeping my fingers crossed that there are no other SMART errors being hidden by this one.