You checked the forecast before you set off outside, and it said 3°C. But when you step outside it feels much colder than that. In fact it feels as though it’s freezing. So, the “feels like” temperature has to be considered when thinking about going out and about on particularly cold days this winter.
What "Feels Like" Actually Measures
A “feels like” temperature reading is a calculation which uses the actual temperature, wind speed and humidity (when relevant) to work out how fast your skin is losing heat. Importantly, the temperature itself never changes due to wind, it is your perception of the temperature that changes. Therefore, this is different to the wind chill figure, which actually measures something different.
A Worked Example: 3°C With Different Winds
This would be demonstrated with an example of a typical UK winter’s day. Taking a temperature of 3°C and increasing the amount of wind, it could be seen how quickly the ‘feels like’ temperature could drop.
Wind speed: Calm or light breeze (around 5mph) – Feels like: roughly 1 to 2°C Wind speed: Moderate breeze (around 15mph) – Feels like: roughly minus 1 to minus 2°C Wind speed: Strong, blustery wind (around 30mph) – Feels like: roughly minus 5 to minus 7°C
The temperature hasn’t changed throughout the day but the rate of heat loss from your body has. This is why walking across an open field or along a coast on a cold and blustery day can feel very harsh whereas on the same day a short stroll around a garden can be quite pleasant.
Why The Figure Sometimes Reads Higher
The “feels like” temperature for cold weather will occasionally appear to rise above the actual air temperature, mainly on calm, clear days. On such days, there is no cooling influence from the wind and there could be a slight warming effect from direct sunlight on skin. In addition, the way we perceive cold air containing high humidity will make it feel cooler than air of the same temperature containing low humidity and conversely warm humid air will feel warmer than similar temperatures of dry air.
What Wind Chill Does Not Do
Many people believe that wind chill will freeze objects and surfaces sooner than the air temperature. However, this is not the case. Wind chill simply tells us how cold it will actually feel for humans, and does not affect the physical world in terms of water freezing and suchlike. So, if it’s 3°C and feels like -6°C, then your car windscreen, outdoor pipes and washing will not freeze any sooner than they would if it was a still 3°C.
How This Connects To Hypothermia Risk
The “feels like” temperature also needs to be taken into account when looking at the risk of hypothermia, as a low temperature and the presence of wind and damp clothing can increase the body’s heat loss. The NHS website provides information on hypothermia and its early signs including shivering, confusion and slurred speech. In addition to this there is a large amount of information available on how extreme temperatures can affect the body in the NHS seasonal health advice for winter.
When To Cover Hands, Ears And Face
Frostbite: This is another hazard of cold weather and is caused by the same wind chill effect as the above temperature reading. It is worth covering up hands, ears, nose and face when the “feels like” temperature drops to around -5°C or below and is strong and blustery. See our page on Frostbite for more information and a full description of the effects as well as advice on how to prevent it. Extremities (such as fingers, toes, nose, ears, face) tend to lose heat most quickly and therefore must be covered up to prevent cold injury. This is why in very cold weather, wearing gloves, a hat that covers the ears and a scarf that covers the lower face is vital.
Simple Checks Before You Head Out
If you know the “feels like” temperature as well as the actual air temperature, you can dress for your journey and school days. For cold days, wearing layers of clothing is better than wearing one thick layer, as trapped air between the layers of clothing is the best way to keep warm. It’s also worth planning school runs, dog walks etc to avoid the worst of the wind. Having spare hats and gloves in the car, in your bag, in the school, etc. can also save cold, sore faces. The UK uses a similar system of weather alerts for cold weather as it does for heat. This is an official system which triggers alerts and advice when the weather is expected to have a severe impact on health.
FAQ
Is the "feels like" temperature the real temperature? No. Air temperature is the temperature recorded by a thermometer and this must not be confused with the ‘feels like’ temperature which takes into account the affect of wind, humidity and even sunshine on human skin.
No. Wind chill only describes how quickly a living body loses heat. It has no effect on physical objects like pipes, windscreens or washing lines, which freeze based purely on the actual air temperature, not the “feels like” figure No, wind chill does not affect physical objects such as car windscreens, pipes and outside washing. These items will freeze at the same temperature as they would on a still day. So a temperature of 3°C with wind is just as bad as a temperature of 3°C without wind for outside activities. However, it does affect how quickly a human body looses heat.
Why is the "feels like" temperature occasionally greater than the actual temperature? Calm air or even sunshine can make the “feels like” temperature read higher than the actual air temperature, for example when there is no wind to carry away the warmth from your skin and you feel the gentle warming of direct sunlight against your skin.
What “feels like” temperature would you cover up your hands and face at? Cover up hands and face when it drops to around minus 5°C or below, especially when it’s also very windy. You can get frostbite to extremities such as your fingers, toes, ears, nose, chin and lips within a short space of time if they are exposed.
