The outdoor temperature displayed in your thermostat's home screen can come either from the sensor in your outdoor unit or from https://www.accuweather.com/. You can choose between these two sources under Menu > Display Settings > Home screen > Outdoor temperature source.
When the AccuWeather option is selected, your Lennox S40 Smart Thermostat must be connected to WiFi.
For more information or a visual representation of steps please reference our user guide here
