Measuring the air temperature accurately isn't as straightforward as you might think.

The current air temperature that you see listed on your phone, computer and TV screens throughout the day is measured inside a special box called a Stevenson Screen.

These enclosures have been used for more than a century and are generally the same shape and design across the world, allowing us to compare observations from different locations and across various periods of history.

Stevenson screens are used to shield temperature sensors from direct sunlight and other elements. This is important because radiation from the sun actually passes through the air without changing its temperature enough for us to perceive. The warmth you feel in the air on a summer's day is actually energy that is being emitted from the ground and other objects around you, after they have been warmed by the sun.

A Stevenson Screen is simply a white box with louvred sides that shields thermometers from direct sunlight, while allowing air to flow freely past the temperature sensor inside. This prevents the thermometer from getting hotter than the surrounding air and allows it to accurately measure the 'air temperature'.

Stevenson screens also shield thermometers from the direct effects of other elements, such as wind, rain, snow and animals.