What is a heatwave?
In 2019, the Met Office issued this guidance for defining a UK heatwave which they state as
A UK heatwave threshold is met when a location records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.
For the United Kingdom the threshold varies, see the UK temperature threshold map below.
Why do heatwaves happen?
Heatwaves are most common in summer when high pressure develops. These systems tend to be slow moving and can persist for a prolonged period of time, such as days or weeks. The jet stream can often be the driver, which is usually located to the UK during summer. This can allow high pressure to develop, resulting in a persistent spell of dry and settled weather.
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 dehydration, which can cause a headache, dizzyness, 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 hayfever, 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 care-givers.
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.