Case study - UK Heatwave, August 2020
The Met Office defines a heatwave as a time when an area experiences very high temperatures for three days in a row. Parts of England and Wales experienced a heatwave between the 7th and the 12th of August 2020. For the first time in over forty years, at least 20 weather stations across the UK recorded temperatures on or above 32°C for six consecutive days.
Causes
The heatwave began when hot, humid air moved over the country from the south. Temperatures in the southern most regions of the UK remained around 34°C for six consecutive days. There were also several tropical nights, which is when night-time temperatures remain above 20°C. The hot weather brought thunderstorms, heavy rainfall and flash-flooding to some parts of the country.
Impact
- The elderly and vulnerable struggled to cope with the hot temperatures. The death rate was higher during the week of the heatwave, although it is unclear how many excess deaths happened because of the high temperatures (deaths from Covid were also a large factor on the death rate of that time)
- Around 300 homes in Sussex were left without running water for days because the heatwave led to an increased demand. Customers in other areas were asked to limit their water use to avoid similar problems elsewhere.
- Many beaches and parks became very busy
- The hot weather led to intense thunderstorms with heavy rain. Firefighters were called out to help with flooding and fire damage from lightning strikes.
- Some roads, for example the M25 around London, were closed due to flash-flooding. The rain also caused landslides in some places. Passengers in Kent had to be evacuated after their train became stuck in a landslide.
Responses
The definition of a heatwave is linked to historical temperature records. Climate change is making the UK much more likely to experience heatwaves than in the past. The country will increasingly have to cope with warmer temperatures and the problems that heatwaves cause.
In response to the increased frequency of heatwaves in the UK, the Met Office have increased the threshold temperature at which a heatwave is declared. Eight counties of the UK have raised the temperature at which a heatwave is declared by 1°C. This change acknowledges that warmer temperatures are to be expected in years to come.