My smartwatch kept failing in the cold – here’s how I fixed heart rate and GPS accuracy

The first time it happened, I assumed it was a one-off. I stepped out into the winter cold, something we know all too well in England, tapped Start on my run, and my smartwatch immediately lost the plot.

My apparent heart rate spiked when I was barely moving, then flatlined, then snapped back to something believable.

GPS wasn’t much better; my pace seemingly lurched up and down, and the route map looked like I’d been zig-zagging.

After a few repeats, it clicked: it wasn’t my fitness or some strange health issue, but the icy conditions.

Cold weather can trip up wrist-based heart rate sensors, and it can make GPS tracking feel less consistent if you rush the start.

The good news? I fixed it with a handful of simple changes and now get accurate readings no matter when I choose to run, walk, or jog.

Why cold smartwatches struggle

Once I stopped questioning my fitness, the pattern made sense. Wrist-based heart rate tracking is optical, relying on getting a clean read of blood flow close to your skin.

In the cold, your body naturally prioritises keeping your core warm, which can reduce circulation in your extremities and make that optical signal noisier and easier to misread.

That’s when you see weird spikes, drop-outs, or a watch “locking on” to something else rhythmic, like your cadence. In simple terms, it's not you, it's the smartwatch.

GPS can feel similarly flaky if you rush the start. Should you begin moving before the watch has a solid satellite lock (something that's very easy to do when you just want to get going), early pacing and the track line can wobble while it catches up.

And, on top of that, manufacturers explicitly note wearable devices have recommended operating temperature ranges, which is worth bearing in mind for proper winter sessions.

Fix 1: Warm the sensor before starting

The biggest change I made was also the easiest. I stopped asking the watch to do its most delicate sensing while my wrists were cold.

If I stepped straight into the cold and immediately started an activity, that was when I’d get the most chaotic heart rate readings. Now, I give myself a few minutes to warm up before I even think about tracking anything.

In practice, that means I’ll walk briskly for five minutes or simply keep my watch tucked under my sleeve until I’m ready to move.

Once my skin’s warmed up a bit, blood flow is more consistent, and the sensor has an easier job, while the heart rate line stops doing that annoying spike-and-drop routine.

Fix 2: Wear your watch properly

The second fix was realising I’d been wearing my watch the “everyday” way, even when the conditions weren’t everyday.

In summer, a slightly looser strap and a lower wrist position can still give you decent results. In the cold, that same setup is basically inviting light leak, movement, and patchy contact.

Now, when it’s cold, I wear the watch a touch higher up my arm, away from the wrist bone, and I tighten the strap so it’s snug without feeling restrictive.

The goal is to have consistent contact. If the sensor is bouncing, twisting, or letting light in, you’re more likely to see those random spikes or drop-outs.

The other winter tweak is layering. If I’m wearing long sleeves, I’ll keep the watch under my cuff so it sits in a warmer pocket of air, rather than exposed to the wind, which might sound obvious but makes a big difference.

Fix 3: Switch to an external heart rate sensor

If the warm-up tweaks help but you still see dodgy readings in the cold, the next step is to stop asking your watch to do everything from your wrist.

For training days where accuracy matters, you can pair your watch with an external heart rate monitor.

A chest strap like the Garmin HRM-Pro is still the most dependable option, because it isn’t trying to interpret blood-flow changes at the surface of your skin, so it’s far less affected by icy hands or the watch moving around.

If you hate the idea of a chest strap, there’s a solid middle ground: an armband-style sensor like the Polar Verity Sense worn higher up the arm.

Fix 4: GPS reliability tweaks that actually help

The quickest GPS win is simply giving your smartwatch a moment to do its thing before you move. Most sports watches will show some kind of GPS indicator – wait until that’s settled, then hit Start.

Additionally, if your watch offers a more advanced GPS mode – usually labelled something like dual-frequency or multi-band – it’s designed to improve consistency in tougher environments, like in tunnels and around cities.

The trade-off is battery life, so you don’t need it for every walk, but it’s worth switching on for sessions where you care about pace accuracy, or you know your route is a bit of a GPS nightmare. Two other quick checks: avoid aggressive power-saving modes during tracked workouts, and try to start in an open area if you can.

Anything else I need to know?

In cold weather, smartwatches aren’t suddenly “bad”: they’re just dealing with weaker signals, more layers, and more chances for the watch to shift around.

A few small habits help. Treat the first minute of any workout as a settling-in period, rather than an instant performance test, and keep the watch in a warmer spot on your arm.

The other mindset shift is knowing what you’re trying to achieve: for easy runs and general fitness, “close enough” is often fine.