This radiator zone is using the external temperature (provided by the weather data) rather than a temperature measured by the system.
For this to happen a number of errors have occurred, such as:
1. A suitable device (such as a Room Sensor or Thermostat) has not been assigned to this zone
2. The temperature measuring device in the zone has developed a fault, such as low batteries or cannot communicate with the Genius Hub
3. The My House Thermostat is not assigned to My House, and so the backup temperature is not available
4. The My House Thermostat has developed a fault which has stopped it communicating a valid temperature recently