Wrist temperature

How your skin temperature at the wrist during sleep differs from your own baseline. Apple Watch measures it overnight on supported models.

Wrist temperature is your skin temperature at the wrist while you sleep, which is related to your body temperature. It's shown as a change from your own baseline, not as a thermometer reading.

You need Apple Watch Series 8 or later, any Apple Watch Ultra or Apple Watch SE 3, sleep tracking with Apple Watch, and Sleep Focus on for at least 4 hours a night. The watch samples two sensors every five seconds while you sleep and turns them into one value per night. Apple Health needs about 5 nights to set your baseline. Apple says it isn't a medical device and can't take a reading on demand. A loose band can throw it off.

It naturally shifts from night to night. Apple lists what you eat, exercise, alcohol, your sleep environment, the menstrual cycle and illness as things that can move it. Studies of wearables find it higher in the second half of the menstrual cycle, and one found it a little higher after shorter sleep.

Pajdo compares each night with your usual nights and only mentions a rise that lasts at least two nights. With cycle awareness on and enough cycles logged, he compares it with the same days of your recent cycles, so the usual second-half rise isn't treated as a change.

This is general wellness information, not medical advice. If a number worries you, or stays away from your usual for a while, talk to a doctor.

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