A fourth heatwave is to hit the UK, bringing a risk of exceptionally severe fires. Temperatures have cooled, winds have picked up and a smattering of rain has fallen for many, but the heat is expected to spike again in the south at the start of the week.
Heatwave Timing and Temperatures
Parts of southern England will yet again meet their heatwave criteria on Wednesday, which could reach highs of 32C or 33C. Others will breach the threshold on Thursday. Exeter was officially in a heatwave for 21 days – a run that will likely end on Sunday.
Health Alert Issued
A yellow heat alert has been issued from 9am on Tuesday to 9am Friday for the East and West Midlands, the south-east, south-west and east of England, as well as Yorkshire and the Humber. The UK Health Security Agency (UKHSA) issued the warning of possible “significant impacts” on health and social care services, including a rise in deaths among the elderly or people with health conditions, and an increase in drownings.
North-South Split
Forecasters are expecting this week’s heat to be a “north-south split”, with clouds and outbreaks of rain continuing in Northern Ireland, Scotland and northern England. But the peak will be “almost a blink and you miss it”, with temperatures widely cooling close to average by the weekend, said Met Office senior operational meteorologist Dan Stroud.
Wildfire Risk and Climate Context
Wildfires, low water levels and drought are a result of the record-breaking temperatures and their longevity, as the UK faces more extreme weather fuelled by human-caused climate change, mostly from burning fossil fuels. July was 3C above average across the UK, according to provisional Met Office data. This could put it among the hottest three or four months of July on record, said Mr Stroud. Southern England has had just 1% of its average July rainfall. England has had 5% and the UK as a whole 20%, according to the Met Office.
Mr Stroud said: “In terms of wildfire, obviously the continuation of the dry and hot conditions does elevate the fire risk. That rain we’ve had, even though it’s welcome rain for the last last few hours, is certainly not enough really to do a huge amount for the dry conditions we’ve already already got. That risk continues.”
Fire Severity Index
If they start, fires are likely to become exceptionally severe on Sunday in pockets of east, south-east and the south of England, according to Met Office data used by Natural England and Natural Resources Wales. That “exceptionally severe” risk level disappears for the whole country before returning on Wednesday for a wider breadth of east, south, and south-east England. It then focuses in the east and south-east of England on Thursday. The Fire Severity Index looks at data including rainfall, temperature and humidity. Agencies use it to assess the severity of fire if it starts. It does not cover the chances of wildfires occurring.
Emergency crews have already spent days fighting large wildfires in Wales and Scotland that forced people to evacuate their homes. Mr Stroud emphasised that the Fire Severity Index measures humidity and drier weather increases the fire risk. The second heatwave was particularly humid and that “does reduce the risk somewhat”. The latest heatwave has been drier and longer-lasting and humidity levels are expected to fall as the fourth heatwave arrives.
