The new Apple Watch series 8 gets a pair of temperature sensors

A lot of doctors consider body temperature — and changes in body temperature — a vital sign. That’s true both to track illnesses but also natural processes in the body, such as ovulation data and menstrual cycle tracking.

Apple added cycle tracking three years ago, and in today’s event, it shared that it has helped 10s of millions of people gain deeper insights into their menstrual cycles and overall health.

The new watch includes a new temperature sensor — two of them, in fact. There’s one temperature sensor on the back crystal near your skin. And another just under the display.

Apple Temperature Sensor

The temperature sensing app on Apple WatchOS. Image Credits: Apple

The two-sensor approach means that Apple Watch is able to isolate your body temperature from the outside environment. That means that the body temperature sensing can be super accurate — Apple claims 0.1°C accuracy, which is pretty spectacular.

Of course, once you have the temperature, you can do a lot of cool things, and Apple does, in the new watch. In the health app, you’ll be able to see nightly shifts from your baseline temperature, which can be caused by things like exercise jet lag, alcohol or illness, but tracking temperature changes is even more useful for those who ovulate because cyclical patterns can reveal the biphasic shift. The biphasic shift is an increase in body temperature that occurs in response to changing hormones, and it can indicate ovulation. If you’re trying to conceive, knowing if and when you ovulated can inform your family planning and conversations with your healthcare provider.

The new WatchOS 9 can notify users of possible menstruation cycle deviations based on what it has learned about your regular cycle. That might mean early detection of pregnancies (whether unwanted or not) and help advise you when the best time would be to try for a baby.

Apple is also doubling down on its privacy, describing it as “a fundamental human right,” and recommits to its commitment to privacy. The company reiterated that cycle tracking data is encrypted on-device and only accessible with a user’s passcode, Touch ID or Face ID. A nod to the company’s dedication to privacy in a post Roe v. Wade world, no doubt.