My Philips kettle will not remain water at exactly 100°C

If the selected keep-warm temperature is 100°C, the kettle keeps the water at a temperature between 90°C and 100°C to avoid excessive steam development.

If the selected keep-warm temperature is 80°, 60° or 40°C, the kettle keeps the water at a temperature between 5°C below and 5°C above the selected temperature.