Electric kettles with water heating up to 90 °C

90 °C (black tea)

— black tea, which is the most common tea variety, has the highest level of fermentation among traditional tea. Typically, the more fermented the tea, the hotter the water required for brewing. However, boiling water is not recommended for brewing black tea since it can harm the taste of the tea and diminish its beneficial properties. There are some methods to bring water to a temperature of 90°C without additional equipment, but to be sure of the exact temperature, it is best to use a kettle with precise temperature control.

In addition, it's worth mentioning that a temperature of 90 °C can also be appropriate for brewing certain oolong tea, which typically have a moderate level of fermentation. The exact degree of fermentation can vary among oolong varieties, and some types with a higher degree of fermentation may require a higher brewing temperature of up to 90 °C.