Apple Watch Series 8 review: temperature-sensing feature will help you warm to it

The Apple Watch Series was once the sole option for iPhone users in the company’s wearable category. Now, it has been sandwiched between the introduction of the SE two years ago and the new Ultra.

But it still maintains its standing as arguably the best option among the three, relative to the fact that the other two are focused on a specific audience — and the new Series 8 aims to continue that momentum.

This year is the first time we have witnessed three Apple Watches unveiled simultaneously. Let’s see what makes it tick this time.

Apple Watch Series 7 and Series 8: what’s the difference?

Physically, nothing has changed. The Apple Watch Series 8 is a clone of the Apple Watch Series 7 as there are no changes in the placement of the digital crown and buttons on the right, and you can still get either a 41 millimetre or 45mm version.

However, the available casing options now are stainless steel and aluminium, with Apple having swapped out titanium for the latter.

While aluminium is the “weakest” among the three options — we are not counting ceramic since it was discontinued in the Series 6 line-up — it is still quite durable and will take a lot of effort to dent.

Users who prefer the reliability of titanium will have to consider the Ultra version. However, stainless steel and aluminium are still good and hold up pretty well.

Display

We have already mentioned the display sizes above and unlike the also-new second-generation Watch SE, both devices have the always-on display — one of the key advantages of the mainstream Watches that has been present since the Apple Watch Series 5.

The feature allows you to see the time and other content — depending on whatever watch face you are using — without having to twist your wrist and angle the device towards your eyes.

The Series 8 retains the maximum brightness of 1,000 nits, which is the same level as the Apple Watch Series 2. Only the Watch Ultra has a way higher number, at 2,000 nits. It is bright enough but, as always, you may have to look closer under direct sunlight.

The health benefits

The Series 8 retains the mainstay health metric measurements, including the third-generation optical heart sensor, a blood oxygen sensor and an electric heart sensor. However, there are a couple of additions that distinguish it from its predecessor.

The first is temperature measurement. The Series 8 has two sensors for this — one on the rear touching the skin and another underneath the display. Apple says this set up was designed to reduce the influence of the outside environment. Do note that this only works with the Series 8 and Ultra versions.

Apple designed the temperature-sensing feature to work best during sleep, measuring changes as small as 0.1ºC every five seconds while you sleep, which is pretty impressive.

However, it won’t be able to measure it in absolute degrees. Instead, it establishes a baseline “normal” temperature — after at least five days of use — then detect any rise or fall.

The changes can be the result of activities such as exercise or things such as jet lag, or even an indicator of illness, and all data can be viewed on the Health app on the iPhone, which, as Apple always stresses, is secure.

Another specific function of the temperature sensor is tied to the Cycle Tracking app for women. Apple says it can be used for retrospective ovulation estimates and improve period predictions.

However, as with Apple’s explicit disclaimer that the Watch is not a medical device and that any health metrics measured with it should only be for reference, the temperature-sensing feature doesn't offer an exact measurement. Consult a doctor if you feel there is something amiss with your health.

Apple has largely avoided attaching “body” to this temperature-sensing feature because it does not do the same job as an actual thermometer.

The second distinguishing feature of the Series 8 is crash detection. Again, to recap: as is the case with the fall-detection feature, it triggers an emergency call and sends messages to your emergency contacts if you are unresponsive for 20 seconds after a crash. This is one of those very good features that we hope no one will ever need to use.

How long does the battery last?

As with every Watch before it, including the new SE, the Series 8’s battery life remains 18 hours. But, again, as is the case with the rest, this is another conservative estimate from Apple.

And similar to the SE yet again, the Series 8 outperforms its advertised timings: from a full charge in the morning, we had no issues until early afternoon the following day. Conservative use had the 10 per cent red alert popping up well into the evening.

The dynamics would change, however, if you use the watch to track your temperature while you sleep. From the same starting point, the low-battery alert flashed at mid-afternoon.

This could be a problem, especially if you still have a long day ahead. In theory, if Apple listed 24 hours, maybe that would be enough to go through two days before reaching for the charger on the second night.

However, you can stretch the battery life with the new low-power mode, which comes with watchOS 9. In case you haven’t read our Watch SE review, here’s a recap: it disables certain functions such as always-on display and other background stuff. You also have the option to keep the mode on for one, two or three days.

Using this, we were good until the evening of the third day, having little left in the tank.

Apple’s Watches are programmed to be used all day and meant to be charged before retiring for the night. Their new function as a sleeping companion could defeat that purpose, so plan your charges accordingly. To give you a hint, we found that they zipped up at 82 per cent in an hour’s charge and crawled to full power a little over half an hour later.

Overall, the Series 8 is good when it comes to battery. We expected it to lag behind the SE, given it has additional background functions; in fact, it did pound-for-pound, but it was completely negligible.

The verdict

Overall, the Apple Watch Series 8 is a minor upgrade from the Series 7. However, the temperature-sensing and crash-detection features are enormous additions, making it the go-to smartwatch for your iPhone if you want full-fledged health features.

This makes us wonder if the Apple Watch is long due for a design overhaul. We have seen this done with the Ultra, but that was done for specific reasons relative to the intended audience. Any changes to the design would be welcome and make it even more appealing for the best-selling smartwatch in the world.