For me, the main feature of the Series 8 is the new temperature sensor, which is supposed to help determine the basal body temperature. This is new to the Apple Watch and only available on the Series 8 and Ultra. The feature helps improve women’s menstrual cycle tracking by informing them of their potential ovulation dates, Apple claims. Apple uses two sensors for this, one on the back of the watch near the skin and a second under the display. The basal body temperature, i.e. the body temperature at rest, shows a slight increase shortly after ovulation. Sometimes the rise is less than 0.5 degrees Fahrenheit. In addition, factors such as stress, jet lag, lack of sleep, etc., affect basal body temperature. The temperature sensor is not designed to measure your body temperature if you suspect you have a fever. It is not calculated in real time. However, if you use the watch daily, you will get an indication of this as the Health app will show the temperature data in detail. This works for men, too. Perhaps Apple could expand the scope of the sensor in the future, but that’s something the company hasn’t confirmed or talked about yet. You must wear the watch at night to sleep for Apple to accurately determine this basal body temperature. The watch must work for at least five nights for the data to be displayed. Note that Apple provides retroactive ovulation data. This should not be used as a method of birth control. An actual ovulation test is the more accurate way to track this. The Apple Watch Series 8, like previous generations, is still the smartwatch to beat for other brands. If you’re an iPhone user and have been wondering if it’s time to get an Apple Watch, the Series 8 is certainly an excellent choice.