Apple Watch Series 8 takes a unique approach to temperature sensing with a two-sensor design — one sensor on the back of the watch, nearest the skin, and another just under the display — reducing bias from the outside environment.
Practically speaking, the Series 8 isn’t all that different from last year’s Apple Watch, or even the one before that. The biggest changes here are the new sensors Apple packed in here, like a system for sensing your temperature, and a specialized motion sensor tuned to detect car crashes.
The second sensor is something I hope you’ll never need to use and can’t really test short of actually crashing a car. (For better or worse, slamming the device onto a hard, carpeted floor wasn’t realistic enough.) But temperature is a different story.
When you look at other observations alongside them, subtle shifts in temperature can sometimes help signal bodily change…
There are actually two temperature sensors in the Series 8: one built into the outer face of the watch, and another in the domed bit that presses into your wrist. But here’s the rub: you can’t use them on-demand the way you would a thermometer. (In other words, don’t buy one in hopes of sussing out the early stages of a fever.)
Instead, those sensors go to work while you sleep in a process that leaves you not with raw temperature numbers, but the variation from your baseline temperature. That baseline, by the way, takes five nights to calculate and remains completely invisible to you.
So far, I’ve been pleased with how accurate the watch’s temperature sensing skills have been.
MacDailyNews Note: Nighttime wrist temperature can be a good indicator of overall body temperature. The sensors in Apple Watch Series 8 sample the wrist temperature during sleep every five seconds and measure changes as small as 0.1° C. In the Health app, users can see nightly shifts in baseline temperature, which can be caused by exercise, jet lag, or even illness.
Utilizing the new temperature-sensing capabilities in Apple Watch Series 8, users can receive retrospective ovulation estimates. Knowing when ovulation has occurred can be helpful for family planning, and Apple Watch Series 8 makes it easy and convenient by providing these estimates in the Health app. Temperature sensing also enables improved period predictions.
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