What is a heatwave?
For a heatwave to occur in the UK, the temperature threshold for that area has to be met or exceeded for at least three consecutive days. The temperature at that location varies by county, from 25°C to 28°C. The chart below shows the current threshold values.
How do we get heatwaves?
Heatwaves are most common in summer as a result of large areas of high pressure. These tend to be slow moving and can last for a long period of time, from days to weeks. The driver for these systems is often the jet stream, which during the summer tends to be north of the UK. This diverts wet low pressure systems away from us, allowing temperatures to build under clear skies and light winds.
Are heatwaves getting worse because of climate change?
Heatwaves are extreme weather events and the latest research from the Intergovernmental Panel on Climate Change (IPCC) shows that climate change is making these events more likely. Heatwaves like the one the UK saw in 2018 are now 30 times more likely to occur than before the industrial revolution due to an increase of carbon dioxide in our atmosphere.
How do I protect myself during the hot weather?
Keeping hydrated is very important. We all sweat a lot more than usual in hot weather, and you'd be surprised at just how much fluid can be lost. Cool drinks will keep you from becoming dehydrated, which can cause a headache, dizziness, cramping or worse.
Public Health England recommends that people stay indoors or out of direct sunlight as much as possible, and particularly when the sun is at its hottest, between 11am and 3pm. Sunstroke can be very serious if not treated quickly, and can easily lead to hospitalisation.
Wear loose-fitting clothes made of light fabrics. Heavier clothes and coats will exacerbate the effects of dehydration and heatstroke.
If you do go outside, apply sunscreen of at least SPF15 with UVA protection, to prevent burning which could lead to skin cancer. You should also wear sunglasses with UV protection - meaning not a pair you bought at the market for £3 - and, if possible, a hat.
Hot weather can trigger strong symptoms in many asthma sufferers - though no one quite knows why. Asthma UK recommends that people should carry their blue inhalers, and take extra care to manage their hay fever, if it's a factor. Air quality can become quite bad with pollution and dust in the air, so sufferers should stay indoors as much as possible.
Dogs die in hot cars; every knows this, but every year it happens. Animals should be kept in cool spaces with space to move around, and given plenty of water. For that matter, children shouldn't be kept in locked cars on hot days either.
Children and the elderly
Hot weather is especially hard for the vulnerable, especially young children or the elderly, and extra precautions need to be taken by parents and caregivers.
Try and keep curtains closed on sun-facing windows, and keep the windows open where possible during the cooler parts of the day. Non-essential lights and electrical items should be turned off as they generate excess heat.