The heatwave is expected to last until the end of the week, and parts of south Wales are likely to see the warmest temperatures throughout the week.
Cardiff was the hottest place in Wales on Monday with a temperature reading of 30.7°C, narrowly beating Sunday's annual temperature record of 30.2C.
More fine and very warm weather is expected this week with a sign of change by the weekend. Here is when the Met Office is predicting the heatwave will end.
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Before that the weather charts show that south east Wales is set to be one of the warmest places in the UK this week.
Weather in your area by postcode:
Monday
Tuesday
Wednesday
Thursday
Met Office forecaster Chris Fawkes said: "The reason our weather pattern is stuck at the moment is because we have got a blocked pattern in the jet stream.
"There is a cut off low to the west. It was one of those that was partly responsible for the catastrophic flooding in parts of Europe. In the UK, we are under a ridge where the weather descends down and collects. An area of high pressure and because the pattern is blocked, we don't see it move around very much.
"There is not going to be much variation day to day."
These maps explain what position the jet steam is in for most of this week:
The jet stream flows high overhead and causes changes in the wind and pressure at that level. If its position ends up to the north of the UK we tend to see calmer, drier weather.
The Met Office explains: "This affects things nearer the surface, such as areas of high and low pressure, and therefore helps shape the weather we see.
"Sometimes, like in a fast-moving river, the jet stream’s movement is very straight and smooth. However, its movement can buckle and loop, like a river’s meander. This will slow things up, making areas of low pressure move less predictably.
"The jet stream can also change the strength of an area of low pressure. It acts a bit like a vacuum cleaner, sucking air out of the top and causing it to become more intense, lowering the pressure system. The lower the pressure within a system, generally the stronger the wind, and more stormy the result."
But like now, the jet stream is slower causing areas of high pressure to take charge.
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