For pure water to boil at sea level, your kettle must heat to 100 °C. Tap water, however, has many impurities, including microbial and organic contaminants in the water.
You may even find chlorine and fluoride too. These, taken in large quantities, can be toxic.
Impurities present in any liquid will raise its boiling point. Thus, it will take a temperature of more than 100 °C to boil tap water in a kettle.