When your system and Google Nest thermostat are working normally, there can be a small difference between what the app and your thermostat show and the temperature you feel. Below are some reasons why.
If your home is very hot or cold, there is probably an issue with your system or thermostat. You can fix many problems with the online troubleshooting widget.
Your thermostat's temperature looks wrong
Your thermostat’s temperature screen will often show you two different temperatures:
- The large target temperature in the middle of the thermostat screen is the temperature that your thermostat was set to either manually or automatically by your temperature schedule. Your system will work to reach and maintain this temperature.
- The small current temperature at the edge of the thermostat screen is the ambient temperature in your home right now.
Note: If your system is on, you’ll also see the estimated time (also known as Time-to-Temperature) it will take for your home to reach the target temperature.
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If you have Farsight enabled
3rd gen Nest Learning Thermostats can use Farsight to show you useful information when you approach. You can have Farsight show you either the target temperature or the current room temperature. If the room seems cooler or warmer than what your thermostat says, Farsight may be set to show you the target temperature, not the current temperature in your home. You can change Farsight settings any time you like.
There's a short delay for turning on your system
It’s normal for your home’s temperature to vary slightly (typically one or two degrees) above or below the temperature set on your thermostat for a short while. This is often due to the built-in delay for turning on your system. This delay is commonly called the maintenance band, deadband, differential, or temperature swing. The delay is usually just a few minutes, but it’s to prevent unnecessary wear on your system and help save energy:
- Many heating and cooling systems have a built-in delay to prevent excessive wear. Since there are moving parts, turning your system on and off frequently may shorten its lifespan.
- Nest thermostats also have a built in delay, like many other thermostats. This is to help save energy and also prevent system wear, especially for systems that don’t automatically delay turning on.
- The maintenance band delay allows the temperature in your home to change by a few degrees before turning on your system, but in most cases you should still be comfortable.
- You’ll know that your thermostat is set to turn on your system by the color of the screen. For example, if the screen is orange, your thermostat is trying to turn on your heat. You’ll also see the temperature screen change color in the app.
Your new Nest thermostat may still be learning
It can take some time for your thermostat to learn your heating and cooling schedule as well as how quickly your home heats up or cools down. So, for the first few days you have it, you’ll need to teach your thermostat what temperatures you like and when. Just turn the temperature up or down on your thermostat or with the app.
If you’ve had your thermostat for a while and it still seems like it’s getting too hot or too cold, try some of the troubleshooting steps below.
Nest thermostat display a rounded temperature
The temperature you see on your Nest thermostat screen and in the app is rounded to the nearest 1°F (0.5°C). Your thermostat uses the unrounded temperature to determine when to turn on your system. So the temperature you see on your thermostat or in the app might change by a few degrees before your system turns on.
That said, all Nest thermostats have multiple temperature sensors that take very precise readings. You can see the unrounded ambient temperature (to the tenth of a degree) : on your thermostat, go to Settings 
Your home takes time to warm up and cool down
Some systems continue running for a short time
Some systems may continue to heat or cool for awhile after they’ve been turned off.
Some systems continue to run the fan to circulate the air that’s left in your ducts or the radiators might stay warm for a while and continue to warm the air in the room. This can cause the temperature to change slightly even after your thermostat stops and cause the temperature in your home to slightly exceed the maintenance band.
You have a Nest Temperature Sensor installed
Most homes heat and cool unevenly, so there can be a fairly large difference between the room where your temperature sensor is and where your thermostat is. So you may notice that the temperature reported by your thermostat and your sensor is different by a few degrees. If the difference is very large, you’ll see an error asking you to move your sensor.
Troubleshooting issues with the Google Nest Temperature Sensor >
Your thermostat or temperature sensor is in a warm or cool spot
Location is one of the most common reasons for a small temperature difference. For instance, if your thermostat is in a hallway near the front door, cold air drafting from outside will make your it think it’s cooler inside. If your thermostat is in a closet or alcove that your system doesn’t warm or cool very well, a Nest Temperature Sensor can help in cases like this. It can tell your thermostat what the temperature is in the room that you’re in, so you’re comfortable there.
If your thermostat is wall mounted, it may be on a wall that’s typically cooler or warmer than the rest of your home. In a poorly insulated or uninsulated wall, warm or cool air may be flowing behind your thermostat. You can patch up or plug this hole to help reduce airflow behind your thermostat. Consult your local building code for materials that you can use to patch this hole safely.