What effect does a heatwave have on mobile phone signal as temperatures soar across the UK?

A cell tower in between two trees. Credit: PA

Words by ITV News Meridian journalist Harry Acton.

As temperatures rise across the UK - with parts of the South East soaring into the 30s this week - many of us will be trying to stay cool.

So why, sometimes, does it feel like when the mercury is rising, your 4G or 5G grinds to a halt?

And why does your device seem to get hot - even when it is out of the sun?

It's more than likely due to demand, as thousands of us descend on locations such as beaches, rivers and lidos during the coming heatwave.

This demand means your phone may be trying various cell towers to get the best signal, heating it up in the process.

How does heat affect my signal?

Weather and cell towers usually get along, but in extreme conditions the RF waves can be disrupted.

These waves are sent between the tower and your phone, allowing you to communicate.

Factors such as humidity and temperature can affect these RF waves, with a higher humidity being linked to weaker signal strengths.

One 2020 study found that higher temperatures actually boosted RF waves and enhanced signal strength.

With the current heatwave, the humidity has remained relatively low - with levels as low as 32% recorded in Winchester on Monday - meaning RF waves had little problem going to and from your device.

What bits of each mast / cell tower do. Credit: Vodafone

Why does my data slow down?

All cell towers have what is called a backhaul.

Berkshire based Vodafone says this backhaul tends to be cables, which are usually fibre optic and connect masts together and to its wider network.

However some more rural and isolated locations may use a microwave dish or have older copper cabling.

This means that if your nearest cell tower is connected via a slower backhaul, it is more prone to slowing down as more devices connect to it.

Distance is also another key factor. For example you may be connected to a tower with 5G - which has a limited range compared to older 4G and 3G - but be at the very end of its range.

The further you are, the more energy the RF waves lose, meaning your connection isn't as strong.

A Vodafone mast in a rural location. Credit: Vodafone UK

As temperatures continue to rise cell towers should continue to function as usual.

The majority across all major networks have extensive air conditioning and cooling for vital equipment - so the risk of overheating is marginal.

It's not to say there won't be infrastructure failures due to the weather, but as more of us take to locations such as beaches to escape the heat, there is a chance that demand causes more of a problem than the weather itself.

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