You check the forecast, see 7 degrees, and dress the way you dress for 7 degrees. Then you step out onto a seafront in a 35mph westerly and are genuinely cold within four minutes.
The air temperature was correct. It was also the wrong number to have looked at. The one that would have told you what to wear was sitting right next to it, and most people scroll straight past it.
What "feels like" actually measures
The Met Office puts it plainly: "Feels like temperature takes into account wind speed and humidity. This makes it easier to understand how the temperature will feel."
That single sentence contains the important detail. It is not a wind chill figure. It accounts for humidity as well as wind, which means it behaves differently in cold weather and in warm weather.
In cold weather, wind is the dominant factor. Moving air strips away the thin layer of warmed air your body holds against your skin, and replaces it with cold air, over and over. The faster the air moves, the faster you lose heat, and the colder you feel at an unchanged air temperature.
In warm weather, humidity takes over. You cool yourself by evaporating sweat. When the air is already close to saturated, the sweat has nowhere to go, evaporation slows, and the same 26 degrees feels considerably more oppressive than it does on a dry day.
This is why the feels-like figure can sit below the air temperature on a windy January morning and above it on a muggy August afternoon. It is doing two different jobs.
The practical rule: in winter, dress for the feels-like temperature, not the air temperature. It is the number that reflects the rate at which you will actually lose heat.
It is not the same as North American wind chill
Wind chill, as most people know it, is a North American index built specifically for cold conditions. It answers one question: how cold does this feel to exposed skin given the air temperature and the wind?
The Met Office feels-like temperature is a broader measure that works across the whole year and includes humidity. The two will often be in the same territory on a cold windy day, but they are not the same calculation, and quoting a US wind chill chart against a UK forecast will give you a number the Met Office never said.
The practical advice that follows from this is refreshingly simple: do not try to do the arithmetic yourself. The Met Office has already done it and printed the answer next to the temperature. Read that one.
Reading wind speed and gusts
Forecasts give you two wind figures and they mean different things.
Wind speed is the mean, the average you can expect at that time. Actual conditions will fluctuate above and below it.
Gust is the highest speed expected between that point in the forecast and the next. Gusts are what knock you sideways, take an umbrella inside out, and make cycling unpleasant, so on an exposed route the gust figure is more useful than the mean.
Worth knowing: the Met Office shows strong winds in bold on its forecasts, and defines that as 25 knots or above, which is 29mph or above. If the wind figure is emboldened, that is the forecast telling you the wind is the main event of the day.
What to wear at a given feels-like temperature
| Feels like | What that actually needs |
|---|---|
| Below 0°C | Base layer, insulating mid layer, windproof outer. Hat, gloves and something over the neck. Exposed skin is the limiting factor, not your torso. |
| 0°C to 5°C | Winter coat with a wind-resistant outer, jumper, hat and gloves. Most people underdress in this band because it does not sound cold. |
| 5°C to 10°C | Jacket over a jumper or fleece. A light hat if it is windy. This is the band where a windproof shell earns its keep. |
| 10°C to 15°C | Light jacket, long sleeves. Something you can take off, because this band swings either way through the day. |
| 15°C to 20°C | Long sleeves or a light layer over a t-shirt. Carry the layer rather than committing to it. |
| Above 20°C | Light, loose clothing. Check the UV index rather than the temperature for whether you need a hat and sunscreen. |
Windproof is not the same as waterproof
A knitted jumper, however thick, is close to useless in wind, because air passes straight through it and takes your warmth with it. A thin windproof shell over that same jumper transforms it, and weighs almost nothing.
All waterproof jackets are windproof, since a membrane that blocks water blocks air. But not everything windproof is waterproof, and dedicated windproof shells are lighter, more breathable and pack smaller than waterproofs. If you are frequently out in dry, windy conditions, a windproof layer is the single most useful thing you can add to a wardrobe.
What matters just as much is closing the gaps. Wind gets in at the neck, the wrists and the hem, and a jacket with a drawcord hem, adjustable cuffs and a collar that actually fastens will keep you warmer than a heavier one that lets air circulate up your back.
Where the wind is worse than the forecast
Forecast wind speeds are for open, exposed ground at a standard height. Your actual experience varies enormously with where you are standing.
- Coasts and estuaries get the full unobstructed wind, and often more of it than an inland forecast for the same region suggests.
- Between tall buildings, wind funnels and accelerates. A city centre can be considerably windier at street level than the number implies.
- Ridges, hilltops and moorland accelerate wind over the top, which is why hill forecasts are issued separately.
- Station platforms, bridges and open car parks are all reliably worse than the surrounding streets.
If your day includes any of those, treat the feels-like figure as optimistic and take the extra layer.
Two habits worth forming
Look at feels-like first, air temperature second. Most weather apps show both. Training yourself to read the right one takes about a week and stops the specific annoyance of being cold in a coat you thought was adequate.
Check the gust figure if your route is exposed. The mean tells you the day; the gust tells you the walk across the car park.
The outfit tool works from the feels-like figure rather than the raw temperature, which is why its suggestions sometimes look heavier than the number would suggest. For the layering system that sits underneath all of this, see the layering guide.