Temperatures in Wales could reach 31°C in Wales on Monday, and the rest of the week is looking "very warm".
But there are signs of a change by the weekend, with temperatures dropping to 20°C and the possibility of thunderstorms. Here is the f orecast for the week ahead.
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Welsh forecaster Derek Brockway tweeted on Monday: "Cardiff Bute Park was the hottest place in #Wales yesterday recording 30.2°C. 31°C predicted today. 23°C in Colwyn Bay.
"More fine and very warm/hot weather this week but signs of a change by the weekend with heavy showers and thunderstorms bringing a drop in temperature."
The Met Office outlook for Wednesday to Friday in Wales says: " The hot weather will continue through this period, with plenty of sunshine, but also a risk of heavy, possibly thundery showers developing each afternoon." Here is h ow beaches and beauty spots looked over the weekend.
Thunderstorms are created by the intense heating of the earth's surface, and are most common in parts of the world where the weather is hot and humid and often come after a heatwave. The Met Office says they develop when the atmosphere is unstable - when warm air exists underneath much colder air.
Check the weather for your area:
Forecasting the weather in Wales, presenter Sue Charles said: "Sunday was the hottest day of the year so far, and a similar day in store on Monday. Any cloud or coastal mist will soon burn away in the strong sunshine. The heat could trigger the odd, isolated shower, more likely across parts of north Wales. For most of us it will be dry, sunny and very warm again. It will stay mild and dry overnight, quite warm for sleeping.
"More of the same on Tuesday. It is later in the week when we will start to see temperatures dropping away. We could see the high moving eastwards with the low pressure bringing the risk of a thundery break down towards the weekend."
The Met Office has shared weather maps of the forecast this week:
Monday
Tuesday
Wednesday
Thursday
Friday
The Met Office forecast is predicting a change by the end of the week and says: "We see a change on Friday as low pressure slowly edges into the south west. Rain and thundery showers arrive in the south west. Some warm sunshine inland elsewhere in the UK. "
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