No wrist temperature data on Apple Watch SE3

"Here’s what you’ll need

• An Apple Watch Series 8 or later, any model of Apple Watch Ultra or Apple Watch SE 3.
• Sleep must be set up with Track Sleep with Apple Watch enabled.
• Sleep Focus must be enabled for at least 4 hours a night for about 5 nights".

in Track your nightly wrist temperature changes with Apple Watch – Apple Support (UK)

If nothing in the get suggestions link try general diagnostics

Apple Watch basic diagnostics - Apple Community

LD150 wrote:

If nothing in the get suggestions link try general diagnostics

Apple Watch basic diagnostics - Apple Community

I read through your Apple Diagnostics post and it's a very useful resource, thanks for making that available.

I noted this: "From watch OS 26 onwards iphone iOS needs to be equal or higher than the watch OS.

i.e. You can use a newer iOS with older watch OS but not the other way round."

When I set up my Apple Watch in December, it immediately updated to 26.2, but my iPhone had not notified me of that update yet so had been on 26.1. A few days later the iPhone updated. Then again, just recently several days ago, the watch updated to 26.3. But my iPhone hadn't yet notified me about an update so I just checked, it is on 26.2.1 still. So I manually looked for an update which was found and it is now updating to 26.3.

But in each instance, the iPhone was "behind" the watch in OS version number. I did not notice any issues and I am not very proactive about these updates, when the watch notifies me I tell it to proceed and likewise the iPhone, but for me just recently, the iPhone showed that an update was available some days after the watch did. So it was "behind" for maybe about a week.

What I learned from your Diagnostics post is that the iPhone needs to be equal to or ahead of the watch in iOS versions, something I was not aware of. I did not notice any undesired results from my iPhone's lag, but now I know to be more careful.

LD150 wrote:

Thebestatech wrote:

version matches

And unpair and set up without backup does nothing?

You will of course need to wait a week or so

Phone on ios18 cannot connect to watch on ios26

I believe that Phone on ios26.2 can connect to watch on ios26.3 so It think it is the major number 10/18/26 that is the key number, not the incremental dot levels

I may mod the tip.

You didn't read the article thoroughly. You lose your saved faces, you lose saved alarms on the watch, and some workout minor settings like split length. All generated data is in Health and in Fitness in the phone via iCloud assuming you didn't turn off Health in iCloud sync settings.

You need to actually use nightly Sleep Schedule.

Originally this was introduced for ovulation tracking.

Thebestatech wrote:

version matches

And unpair and set up without backup does nothing?

your data would have been synced to the health and fitness apps on the iphone connected to the watch