UK extreme heat: expert explains May temperature swing

Temperatures across the UK are forecast to reach 30°C over the bank holiday weekend. 

Professor Hannah Cloke, Regius Professor in Meteorology and Climate Science at the University of Reading, explains why. 

Read more: New Regius Professor puts people at heart of climate debate

For interviews, contact the University of Reading Press Office on 0118 378 5757 or pressoffice@reading.ac.uk. 

Regius Professor Hannah Cloke, University of Reading, said: "After a chilly and disrupted start to May, the UK's weather is about to take a very different turn. A large, stable block of high pressure is settling over western Europe, and it is this that is the primary driver of what we are about to experience. As air sinks beneath it, it heats up through compression, pushing surface temperatures well beyond what we would expect at this time of year. This is then further intensified by very warm air being drawn in from north Africa and the Iberian Peninsula, as well as strong solar heating as we approach the longest days of the year. When conditions are stable enough, this kind of pattern can persist for days or even weeks, preventing the cooler Atlantic weather that usually keeps British summers in check from breaking through.

“For parts of south-east England, we could be looking at 30°C, a threshold rarely crossed in May. While daytime temperatures will be exceptional, nights are likely to stay cooler, giving some crucial respite for people who are particularly vulnerable to heat.

“For farmers, a prolonged spell of heat and dry weather at this stage of the growing season brings real concern. Many crops are at a critical point of development and sustained high temperatures, combined with a lack of rainfall, can cause stress, reduce yields and in some cases cause irreversible damage. Parts of Europe are already dry after a below-average spring, which makes this episode particularly poorly timed.

“Spells of extreme heat like this are a reminder of why adaptation to a warming climate cannot wait. A report published this week by the Climate Change Committee warns that without urgent action, the majority of UK homes will overheat by 2050, water shortages will worsen and the costs to public welfare could reach hundreds of billions of pounds a year. The solutions exist. The challenge now is turning adaptation plans on paper into streets, homes, rivers and infrastructure that are ready for what’s coming.”

Data from the Reading University Atmospheric Observatory: 

Dr Jess Neumann, associate professor of hydrology at the University of Reading, said: 

“Hot weather should not be underestimated. There were more than 1000 excess heat-related deaths in the UK last year. People are urged to take care during hot weather by staying hydrated, carrying spare water on journeys, wearing adequate sun protection and seeking shade or cool spaces.

"Big questions are already being asked about what another potentially hot and dry summer might bring.

“While current water levels are largely ‘normal’ for the time of year, there are concerns around the potential for drought if warm and dry conditions continue over the coming weeks and months.

"The direct impacts of low rainfall on society may not be felt for a while, but the effects of low rainfall on rivers, wildlife and our environment are already in motion. Many rivers already have notably low flows, increasing pressure on aquatic life and raising concentrations of water pollutants harmful to wildlife and human health.

"It is never too late to be mindful of our water use. Hot weather increases demands on water resources. Small actions such as turning off taps, collecting rainwater for use on plants, using a watering can and taking shorter showers can all help reduce our individual water footprints."