Will the thermostat still control my heating and cooling if my Wi-Fi connection is lost?

Yes, the thermostat will operate your heating and/or cooling system with or without Wi-Fi. If the no-Wi-Fi indicator appears in the upper right corner of the home screen, you can try restarting the thermostat by removing it from the wallplate, waiting 10 seconds, and snapping it back on. Note that if you are not connected to Wi-Fi, you will not receive automatic software updates. (Pages 55 and 58)