Hospital operations have made the decision to cancel operations due to “very high temperatures”.
The highest alert level warns that fit and healthy people could become ill and even die due to the extreme heat.
Joe Harrison, CEO of Milton Keynes University Hospital, said: “We have made the decision to cancel routine outpatient appointments and surgeries on Monday and Tuesday as many of the patients traveling to these appointments are frail and at increased risk and due to the unpredictable nature of very high temperatures when needed for emergency care and care environments.”
“We will do everything we can to keep the wards and departments as cool as possible, but we know this will be a challenge given the very high temperature outside.
“We have solid plans and contingency plans in place and will keep social media channels and our website updated with any changing information.”
A national emergency should only be declared when a heatwave is “so severe” or “prolonged” that its impacts go beyond the health sector – which is currently the case under pressure due to rising temperatures.
The Met Office has issued a rare red alert for many parts of England, meaning the extreme weather could result in “serious illness or danger to life”.