Issued with public health partners, the warning will run until Thursday.
Met Office Chief Operational Meteorologist Steven Ramsdale said: "The impacts of extreme heat can be many and varied. It can have health consequences, especially for those who are particularly vulnerable, and it can impact infrastructure, including transport and energy, as well as the wider business community.
⚠️⚠️ Amber Weather Warning issued ⚠️⚠️— Met Office (@metoffice) July 19, 2021
Extreme Heat across parts of South Wales, West Midlands, southern and southwestern England
Valid until 23:59 Thursday
This is the first ever Extreme Heat Warning issued#Heatwave
Latest info 👉 https://t.co/QwDLMfRBfs
Stay #WeatherAware pic.twitter.com/bTHUyFL6uL
"During hot weather we often see increased traffic near coastal areas, increased use of open water by the public, and an increase in wildfire risk."
Much of the UK has been in heatwave conditions in recent days, but temperatures are expected to climb further early this week, possibly reaching 33C in some western areas, but widely high 20s and low 30s elsewhere. Parts of Shropshire are expected to hit 29 degrees.
“The high temperatures are going to continue through a large part of this week. Many areas will continue to reach heatwave thresholds but the amber extreme heat warning focusses on western areas where the most unusually high temperatures are likely to persist.
“There’s a continuing risk of isolated thundery downpours late in the afternoons but most areas will stay dry until later in the week. Temperatures should begin to fall for most areas heading into the weekend, with some more unsettled conditions looking to develop.”