Summer 2021 will mark a turning point in how heat is seen by the public and communicated by experts. For the first time in its 167-year history, the UK’s Met Office has issued an amber warning for extreme heat for much of Wales and parts of southern, central and western England, where temperatures are expected to reach 33°C in places.
It’s an exciting time to be a researcher specialising in heat. I’ve spent a lot of my time so far explaining to people that heat is an invisible killer that can affect every aspect of our lives. The Met Office’s new heat warning service, if communicated well, could change the public’s often risky relationship with heat for the better and save lives.
The Met Office was spurred by the deaths of nearly 2,500 people during three heatwaves in the UK summer of 2020 to change the way it forecast hot weather. That was the largest number of deaths related to heat since Europe’s August 2003 heatwave.
Until now, heat warnings for England have been issued under the Public Health England-funded heat health plan. These warnings are only communicated to those working in the health sector, to protect vulnerable people.
This system has a lot of gaps. For example, its vulnerable definition doesn’t capture everybody, because vulnerability is something that changes for all of us at different points in our lives. This is particularly true of those who live alone or have a mental health condition, and tend to be missed. Many vulnerable people don’t see themselves as at risk.
Extreme heat forecasts
For the moment, the Met Office continues to use temperature alone to indicate an extreme heat warning, whereas relative humidity, wind speed and how much sun we get all influence extreme heat levels. A warning is triggered when a part of the UK is forecast to have a 70% likelihood of exceeding a heat threshold, defined by the average summer climate of each UK region, for two days consecutively and one night in between.
Here’s the confusing part. This definition of an extreme heat event is different from the scientific definition of a heatwave originally set by the Met Office: when conditions exceed the average for three days in a row and two nights in between. The revision is important because extreme heat affects health before it has been long or hot enough for conditions to be classified a heatwave.
How to beat the heat
If your area is subject to an extreme heat warning, do not panic. There are lots of ways to avoid heat stress, which can cause lethargy, diarrhoea and headaches. Please take medical advice where necessary from NHS 111 or your GP, and call 999 in an emergency.
- Keep cool. If indoors, trying bathing your feet in cold water or have a shower. If you have a garden, paddling pools are a good way to cool down. If you are an experienced swimmer and want to go swimming outdoors, do not go alone and be careful to ease yourself into the water slowly, somewhere shallow. Cold shock from jumping into deep water is a very serious risk – six people have drowned so far in 2021 because of this.
- Stay hydrated. Humans are mostly water and we lose a lot of this in heatwaves through sweat. Drink more often than you usually would, even when you don’t feel thirsty. If you don’t like water, squash is good to replenish the minerals your body needs. When enjoying alcohol or caffeinated drinks, make sure to keep drinking water too.
- Cool your house down. Close the curtains and open windows on the side not facing the sun. If you have a kitchen extractor fan, turn it on. If you live in a block of flats and feel comfortable doing so, leave your front door open. This all helps to keep air flowing through your home.
- Be heat-aware. Look out for over 65s, pregnant women, children under five and those with medical conditions. These groups are all more vulnerable to heat. You should also avoid being in direct sunlight between 12pm and 3pm when the sun is at its strongest.
- Be aware of other risks. Sunburn and high levels of air pollution are both more likely during heatwaves. There are also risks unrelated to health, such as train signal failures that can disrupt daily life.
Heat in a changing climate
Heatwaves are becoming more frequent, longer and intense as a result of climate change. Extreme heat warnings will be an important part of adapting to climate change. But it is only when forecasts are combined with adaptation measures, led by government and communicated effectively through official channels, that this risk will be addressed.
Heatwaves internationally need more research funding and better communication. Weather extremes such as flooding have been extensively studied and the subject of warnings for over 30 years. The Met Office extreme heat warning system gives hope that soon heat will be treated more seriously.