I have my router and server set up in the garage. Mine is an old house and it's not possible (without a considerable expense) to get the ONT and cabling moved. So I have the router in the garage (cinder block walls, concrete base, no insulation), and have had this setup for the last 11 years. I have started off with the original Verizon FIOS modem, then the RT-AC86U and now the RT-BE88U. Ran Cat6 from the garage to two end-points within the main house and have setup an AiMesh. The router in the garage also transmits WiFi which is used by the security cameras, car, charger and other IoTs. Have had zero issues. I am in Westchester county, NY. So it does not get really cold, though this winter was about -20F for a stretch.