The yellow status means the hot weather has:- "potential for significant impacts" across the health and social care sector with a risk to those who are particularly vulnerable.
UV levels and pollen levels are also set to remain high all week, meaning sun cream and for hayfever sufferers should expect to use antihistamines.
While the weather is expected to get cooler and cloudier by the end of the week, the Met Office says there is uncertainty about how quickly that change will take place.