What is the ‘feels like’ temperature and how is it calculated?

It’s a mistake we’ve all made – leaving the house thinking it’s warmer outside than it actually is and regretting leaving our winter layers behind.

As winter arrives and a strong cold front makes its way across the country’s east, Australians are extra reliant on knowing just how brisk will be when they’re out in the elements.

But if you often feel far colder than what the weather forecast has warned you to expect, there’s another temperature measurement you should be considering: the “feels like” temperature.

What is the ‘feels like’ temperature?

As the name suggests, the “feels like” temperature is how we’re going to feel when we venture outdoors.

The daily temperatures we see on our smartphones, in our cars and at the end of the nightly news take into account the air temperature, which is measured in isolation by a thermometer that is sheltered from the wind, rain and sun – also known as a Stevenson screen.

West Island BoM Officer in charge Alana-Jayne Moore conducts observations.
It might not look like much, but this is how the BOM measures temperatures. (ABC Radio Perth: Emma Wynne)

Although it’s a useful measurement, it doesn’t take into account other factors that impact how we experience temperature, like humidity and wind (but more on those later).

Basically, you can consider the “feels like” temperature to be an indication of how comfortable we’re likely to feel when we’re outside.

How do you measure what it ‘feels like’?

It’s more than just the vibe of the great outdoors. The Bureau of Meteorology (BOM) has a mathematical equation to estimate what it actually feels like for an average person outside.

It takes into consideration the actual air temperature recorded, along with the humidity and the wind speed to determine the apparent temperature, which is what we know as the “feels like” temperature.

If you’re interested in what that looks like, here’s the equation.

AT = Ta + 0.33E – 0.70WS – 4.00

Don’t worry if maths isn’t your strong suit. The BOM helpfully crunches the numbers for us, so all we have to do is decide whether to grab a jacket before taking the dog for a walk.

A woman dressed in black with a white hat and a mask walks a ginger dog.
Temperatures have plummeted across eastern Australia as a cold front crosses the country. (ABC News)

But there are some important assumptions that the BOM makes in calculating what the temperature will feel like when we’re out and about.

The BOM bases the “feels like” temperature on an adult that is appropriately dressed for the season – that means no T-shirts and shorts in the middle of a Victorian winter, for example – and assumes they are outside walking in the shade, not direct sun.

That’s because being in direct sun can increase the “feels like” temperature by about 8 degrees Celsius, so using shade ensures there is more consistency in the measurement.

Two people walk on the grass in the morning fog at Birdsland reserve, in Belgrave South.
Wind chill can make us feel colder than what has actually been forecast. (AAP: Joe Castro)

Why does the temperature feel different?

Both humidity and wind affect how we experience the air temperature, or what’s been forecast for the day.

For example, we will often feel colder when the wind is stronger. That’s because the wind strips away the thin warm layer of air that we naturally have around our bodies to keep us comfortable.

When that disappears, our skin is more exposed, and that makes us feel colder as a result.

But when the humidity is higher, it becomes harder for our sweat to evaporate, which would otherwise keep us cooler.

By factoring in wind and humidity, we get a more complete picture of the “feels like” temperature – an important indicator as we prepare to shiver through the next few months.

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