Can the Apple Watch Ultra read surface body temperature?

It is a strange sensor… apple says that it reads the temperature of your wrist every 5 seconds…. But nothing of these measurements can be seen. So you cannot see your wrist temperature, or the changes in that, over the whole night. The only thing that you can see is (1) one average measurement over the whole night.. That is quite a waste.

It can be very sufficient in tracking the women’s cyclus temperature, but for most others it does not make sense…. Except when you have a fever, but that is mostly very clear to one.

I could not find much information about temperature sensing, the only note on the Watch Ultra web pages seems to be

Temperature sensing. An innova­tive temperature sensor9 enables groundbreaking insights for women’s health and advanced cycle tracking.10 And it records overnight temperature changes, which you can see in the Health app.

As such it appears to be aimed at Women's health issues and there is no obvious comment whether it can do more general temperature sensing. I would also doubt the ability to get accurate temperature while immersed in water (implies swimming) because the colder water is likely to get between the human and the watch so it might show water temperature rather than skin temperature. It would of course be completely unable to measure body core temperature in these conditions.

I think my answer is close to very correct. You only see one digit per day, exactly as shown in your scheme.

where are the other 5x60x8 measurements.

In this way temperature has only one purpose and that is for the cycle tracking of women.

For others who might want to see all other measurements the temperature sensor has no purpose at all.

I don't think Apple said this was for looking after people with a fever and has nothing to do with temperature while in water (the topic) but if it answers the author's question no doubt they will award you kudos as necessary.

But yes it is designed primarily for menstrual cycle tracking during sleep. That is a positive not a negative bearing in mind the general neglect of womens' needs in tech over the last decades.

From a purely scientific point of view the skin temperature will be severely compromised by the water temperature, particularly in unheated pools or open water.

If it did measure it it would be misleading. Hopefully it will have common sense programmed in to turn it off.

You need to read this article below which showd that your statement about only showing average is incorrect

Track your nightly wrist temperature changes with Apple Watch - Apple Support

PS it's Apple Watch, it never has been an iwatch. 🤓