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

Home Hub Command Center with Dome Base Feature

Apple Working on All-New Operating System

Thursday September 25, 2025 1:11 pm PDT by
Apple is developing an all-new operating system codenamed "Charismatic," according to Bloomberg's Mark Gurman. Apple smart home hub concept based on rumors This is likely Apple's long-rumored "homeOS" operating system. In a report last month, Gurman said both Apple's rumored smart home hub in 2026 and tabletop robot in 2027 will run the new operating system. He said the software platform ...
Tim Cook Rainbow

Apple Event in October? Here's What to Expect

Monday September 29, 2025 9:31 am PDT by
Apple's annual iPhone event is in the rearview mirror, but rumors suggest the company plans to release a handful of additional products before the year ends. Will there be another Apple event this October? We discuss the possibility below. Apple in October Apple's most recent October events were in 2021 and 2023. In 2022 and 2024, Apple did not host an October event. Instead, it...
iOS 26

Apple Continues to Prepare iOS 26.0.1 With Multiple Bug Fixes Expected

Sunday September 28, 2025 1:30 pm PDT by
Apple is preparing to release iOS 26.0.1, according to a private account on X with a proven track record of sharing information about future iOS versions. The account initially said iOS 26.0.1 would have a build number of 23A350, but they now expect the update to have a build number of 23A355. This suggests that the software update will include more bug fixes or changes than initially...
Apple MacBook Pro M4 hero

New MacBook Pro Nears Mass Production, But Four Bigger Upgrades Expected Next Year

Sunday September 28, 2025 2:08 pm PDT by
Apple's next MacBook Pro models will enter mass production soon, according to the latest information shared by Bloomberg's Mark Gurman. In his Power On newsletter today, Gurman said he continues to believe the new MacBook Pro models will be released at some point between late 2025 and the first quarter of 2026, meaning they should be available to order by March at the latest. Apple often...
iOS 26

Apple Releases iOS 26.0.1 With Fixes for Wi-Fi, Cellular, and Camera Issues on iPhone 17 Models

Monday September 29, 2025 10:12 am PDT by
Apple today released iOS 26.0.1 and iPadOS 26.0.1, the first updates to the iOS 26 and iPadOS 26 operating systems that came out earlier this week. The new software can be downloaded on eligible iPhones and iPads over-the-air by going to Settings > General > Software Update. According to Apple's release notes for the update, iOS 26.0.1 addresses a bug that could cause aberrations in...
iOS 26 Battery Glass Feature

iPhone 16 Pro Max 80% Charge Limit: One Year Later, Was It Worth It?

Wednesday September 24, 2025 3:58 pm PDT by
With the iPhone 15 series, I did an experiment and kept my iPhone's Charge Limit set at 80 percent for an entire year. It provided an interesting look at the impact of charge limits on battery longevity, so I decided to repeat it for the iPhone 16 line. Since September 2024, my iPhone 16 Pro Max has been limited to an 80 percent charge, with no cheating. As of today, my battery's maximum...
iphone 17 ceramic shield

Regular iPhone 17's USB-C Charging Speeds Tested With Apple Chargers

Friday September 26, 2025 9:01 am PDT by
The website ChargerLAB has tested the standard iPhone 17 model's USB-C charging speeds with a variety of Apple's chargers, from 18W to 140W. The device reached a peak charging speed of around 27W to 28W with these Apple chargers:29W USB-C Power Adapter 30W USB-C Power Adapter 35W Dual USB-C Port Power Adapter 35W Dual USB-C Port Compact Power Adapter 40W Dynamic Power Adapter with 60W Max...
LG UltraFine 6K Display TB5

LG UltraFine 6K (32U990A) TB5 Display: Pre-Orders Open September 30

Monday September 29, 2025 6:21 am PDT by
Pre-orders for LG's new UltraFine evo 6K display (model 32U990A) with Thunderbolt 5 support will begin on September 30, according to a major U.S. retailer listing. LG first revealed the 32-inch display at CES 2025 in January, teasing its status as the first monitor to support Thunderbolt 5. At the time, LG only provided high-level specs, but left pricing, availability, and full technical...
AirPods Pro 3 Newsroom

Apple's 'Back to School' Offer Ends Soon, Now Applies to AirPods Pro 3

Wednesday September 24, 2025 7:20 am PDT by
Apple's annual "Back to School" promotion for students ends soon, so act fast if you want to score free AirPods with the purchase of an eligible new Mac or iPad. Until Tuesday, September 30, college students and qualifying educational staff in the U.S. can receive free AirPods 4 with Active Noise Cancellation when they purchase an eligible new Mac or iPad from Apple. This is a $179 value. ...

Top Rated Comments

Le0M Avatar
40 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
40 months ago
I just wish it could last 5 nights on a single charge… ?
Score: 9 Votes (Like | Disagree)
dz5b609 Avatar
40 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
40 months ago
So it won’t alert me if I have a fever?
Score: 7 Votes (Like | Disagree)
whoknows2597 Avatar
40 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
40 months ago
For those that wear your watch overnight, when do you charge it?
Score: 5 Votes (Like | Disagree)