Apple Watch Series 8's Body Temperature Sensor Won't Do What You Think

The body temperature sensor rumored to come to this year's Apple Watch Series 8 models is not expected to offer exact measurements, according to multiple reports from reliable sources.

Body temperature monitoring for the Apple Watch has long been rumored by sources like Apple analyst Ming-Chi Kuo, but over the past year rumors have crystalized around the feature finally debuting on the Apple Watch Series 8 later this year. Just last week, Apple was granted a patent for a temperature sensor conspicuously related to the Apple Watch. Contrary to the hopes of some observers hoping to be able to check their body temperature or see if they have a fever, it looks like the feature may be significantly more limited at launch.

Reports from the Wall Street Journal and Bloomberg's Mark Gurman state that the body temperature sensor is primarily designed to aid fertility planning, giving women insights into their ovulation cycle, and could be used to improve the detection of patterns when tracking sleep. Apple significantly bolstered the Apple Watch's sleep tracking capabilities in watchOS 9, so further improvements in this area aided by hardware this year seem plausible.

Apple is also said to have plans to enable the body temperature sensor to detect when a user has a fever, but it seems unlikely that this feature will be available upon the launch of the Apple Watch Series 8. Gurman believes that further in the future, Apple Watch models could determine if a user has a higher than normal body temperature, but it is still unlikely to show an exact measurement. All in all, this suggests that the body temperature sensor that comes with the Apple Watch Series 8 may not be quite what some users have come to expect.

According to Kuo, Apple originally intended to offer a body temperature measurement feature with the ‌Apple Watch Series 7‌ models, but the company shelved the plans when the body temperature algorithm it had developed failed to meet requirements before the device entered the engineering validation testing (EVT) phase last year.

The problems Apple has experienced relating to body temperature measurement purportedly relate to the fact that skin temperature quickly varies based on the environment, and since a smartwatch cannot monitor core body temperature using hardware, the feature is heavily dependent on an algorithm that produces accurate results. This likely explains why the body temperature sensing capabilities of the Apple Watch may be limited when the Series 8 launches later this year.