Illegal in Garbage & Drains
A thermometer that contains mercury should be disposed of as Household Hazardous Waste (HHW), so never throw them in the trash. If the thermostat is digital then the batteries should be treated as e-waste. If the thermometer is not digital and does not contain mecury it can be thrown away.
You can drop off thermometers at the Eastern Regional Landfill year-round without an appointment.