Apple Watch Series 8 Takes Five Nights to Establish Baseline Wrist Temperature

Apple today published a new support document with additional details about the new wrist temperature sensing feature available on Apple Watch Series 8 and Apple Watch Ultra models, and it turns out the feature requires users to wear their watch for five nights before it can detect a baseline temperature.

apple watch series 8 trio
Apple Watch Series 8 and Apple Watch Ultra have two temperature sensors — one on the back crystal, near your skin, and another just under the display. While the wearer sleeps, Apple Watch samples wrist temperature every five seconds. This design improves accuracy by reducing bias from the outside environment, according to Apple.

Your body temperature naturally fluctuates and can vary each night due to your diet and exercise, alcohol consumption, sleep environment, or physiological factors such as menstrual cycles and illness. After about 5 nights, your Apple Watch will determine your baseline wrist temperature and look for nightly changes to it.

Apple says that Sleep must be set up with "Track Sleep with Apple Watch" enabled, and Sleep Focus must be enabled for at least four hours a night for about five nights. After that, users can check Body Measurements -> Wrist Temperature in the Health app for recorded measurements.

Apple cautions that the feature isn't a medical-grade device and shouldn't be used for any medical purpose, nor is it a thermometer, and it cannot provide measurements on demand. A loose-fitting Apple Watch can also impact wrist temperature data.

Apple is marketing the feature in promotional materials for the new Apple Watch models as a way to improve period predictions and retrospective ovulation estimates, but the support document suggests that tracking nightly temperature changes while sleeping can give anyone insight into their "overall well-being."

For those who have no use for the feature, Wrist Temperature can be turned off in the Watch app on iPhone, under Privacy -> Turn off Wrist Temperature.

Related Forum: Apple Watch

Popular Stories

AirPods Pro 3 Mock Feature

AirPods Pro 3 Just Months Away – Here's What We Know

Friday April 18, 2025 5:16 am PDT by
Despite being more than two years old, Apple's AirPods Pro 2 still dominate the premium wireless‑earbud space, thanks to a potent mix of top‑tier audio, class‑leading noise cancellation, and Apple's habit of delivering major new features through software updates. With AirPods Pro 3 widely expected to arrive in 2025, prospective buyers now face a familiar dilemma: snap up the proven...
iphone 16 pro models 1

17 Reasons to Wait for the iPhone 17

Thursday April 17, 2025 4:12 am PDT by
Apple's iPhone development roadmap runs several years into the future and the company is continually working with suppliers on several successive iPhone models simultaneously, which is why we often get rumored features months ahead of launch. The iPhone 17 series is no different, and we already have a good idea of what to expect from Apple's 2025 smartphone lineup. If you skipped the iPhone...
ipad air windows 11 arm

M2 iPad Air Runs Windows 11 ARM via Emulation, Thanks to EU Rules

Tuesday April 22, 2025 5:01 am PDT by
A developer has demonstrated Windows 11 ARM running on an M2 iPad Air using emulation, which has become much easier since the EU's Digital Markets Act (DMA) regulations came into effect. As spotted by Windows Latest, NTDev shared an instance of the emulation on social media and posted a video on YouTube (embedded below) demonstrating it in action. The achievement relies on new EU regulatory...
iphone 17 air dummy unbox therapy

iPhone 17 Air's Extreme Thinness Demoed in New Video

Tuesday April 22, 2025 10:22 am PDT by
Apple plans to release an all-new super thin iPhone this year, debuting it alongside the iPhone 17, iPhone 17 Pro, and iPhone 17 Pro Max. We've seen pictures of dummy models, cases, and renders with the design, but Lewis Hilsenteger of Unbox Therapy today showed off newer dummy models that give us a better idea of just how thin the "iPhone 17 Air" will be. The iPhone 17 Air is expected to be ...
iOS 18

iOS 18.5 Includes Only a Few Changes So Far

Monday April 21, 2025 11:00 am PDT by
Apple seeded the third beta of iOS 18.5 to developers today, and so far the software update includes only a few minor changes. The changes are in the Mail and Settings apps. In the Mail app, you can now easily turn off contact photos directly within the app, by tapping on the circle with three dots in the top-right corner. In the Settings app, AppleCare+ coverage information is more...
maxresdefault

iPhone 17 Pro Launching Later This Year With These 12 New Features

Sunday April 13, 2025 7:52 am PDT by
While the iPhone 17 Pro and iPhone 17 Pro Max are not expected to launch until September, there are already plenty of rumors about the devices. Subscribe to the MacRumors YouTube channel for more videos. Below, we recap key changes rumored for the iPhone 17 Pro models as of April 2025: Aluminum frame: iPhone 17 Pro models are rumored to have an aluminum frame, whereas the iPhone 15 Pro and ...
Beyond iPhone 13 Better Triad

Apple's 20th Anniversary iPhone May Finally Go All Screen

Tuesday April 15, 2025 6:31 am PDT by
Apple is preparing a "bold" new iPhone Pro model for the iPhone's 20th anniversary in 2027, according to Bloomberg's Mark Gurman. As part of what's being described as a "major shake-up," Apple is said to be developing a design that makes more extensive use of glass – and this could point directly to the display itself. Here's the case for Apple releasing a truly all-screen iPhone with no...
CarPlay Hero

Apple Releases Wireless CarPlay Fix

Wednesday April 16, 2025 11:28 am PDT by
If you have been experiencing issues with wireless CarPlay in your vehicle lately, it was likely due to a software bug that has now been fixed. Apple released iOS 18.4.1 today, and the update's release notes say it "addresses a rare issue that prevents wireless CarPlay connection in certain vehicles." If wireless CarPlay was acting up for you, updating your iPhone to iOS 18.4.1 should...

Top Rated Comments

Le0M Avatar
34 months ago
Honest question:
If I wear the watch all day, and put it into charge before going to sleep, how can I possibly be wearing it at night?
Score: 10 Votes (Like | Disagree)
PowerButton Avatar
34 months ago
I just wish it could last 5 nights on a single charge… ?
Score: 9 Votes (Like | Disagree)
dz5b609 Avatar
34 months ago

Honest question:
If I wear the watch all day, and put it into charge before going to sleep, how can I possibly be wearing it at night?
Because there's quick charging on the newer ones which means that 15-30 minutes of charging in the evening will get you through the night and 15-30 minutes of charging in the morning (while showering for example) will get you through a day (because it will still be pretty charged from that evening 15-30 minute charge).

Added bonus of that is that's very good for your battery health.
Score: 9 Votes (Like | Disagree)
Corsig Avatar
34 months ago
So it won’t alert me if I have a fever?
Score: 7 Votes (Like | Disagree)
whoknows2597 Avatar
34 months ago

Came here to ask this as well. I dont sleep with mine on because obviously it has to get charged at some point and a watch doesnt do me much good on a charger during the day?!
What I do, take off my watch an hour or so before my bedtime then do my evening routine. After that time, it should be 80% to 100% charged then I wear my watch when sleeping. In the morning, I place it on the charger and leave it there before I head out to work.
Score: 7 Votes (Like | Disagree)
performa_6400 Avatar
34 months ago
For those that wear your watch overnight, when do you charge it?
Score: 5 Votes (Like | Disagree)