A "plume of tropical air" will send temperatures soaring in North Wales - but the hot conditions will not last long.
Forecasters are predicting that the mercury will rise to around 27C in some parts of the region by Friday, which is as hot as current forecasts for Tenerife on the same day.
But the mini heatwave will not last too long, with temperatures falling back into the mid-teens by the weekend.
BBC weatherman Derek Brockway said on Twitter: "A plume of tropical air will bring toasty temperatures next Friday.
"Mid to high 20s Celsius in Wales.
"But the summer heat will be brief.
"Temperatures drop nearer normal again over the weekend."
Ahead of the warm end of the week, people will have to endure further spells of heavy rain and cooler conditions.
The Met Office said: "It will be a wet and windy day [on Monday] with heavy rain slowly moving northeastwards through the morning.
"Scattered locally heavy showers will develop behind the rain before easing towards evening.
"Feeling cool in the rain.
"Tuesday will be mostly dry but cloudy at times, though with a few showers possible. Sunny spells will develop towards evening.
"The next few days will be largely dry with sunny spells, though Thursday may see some heavy rain across northern parts with brisk winds.
"A brief very warm spell is likely for many areas at the end of this week with a good deal of sunshine, although increasing cloud may bring rain to the northwest.
"It may become hot in southeastern areas."
Following the warm spell, thunderstorms and showers are set to return to the region this weekend, with more unsettled conditions on the way in the following week.
The Met Office said: "Scattered showers and thunderstorms will probably introduce cooler, more changeable conditions from the west next weekend.
"Through early August changeable weather is likely to continue with bands of rain, perhaps accompanied by strong winds, interspersed with brighter, showery conditions.
"However, all areas should have some dry spells, these most likely in the east, with a better chance of dry spells more generally late in the period."
