Saturday will be a scorcher with temperatures hitting 41 C inland and extreme high temperature in force from 11 am until 5 pm.
There will be little respite in the next few days, with temperatures forecast to remain at the same levels until Tuesday.
In its early morning weather forecast, the Met Office said that Saturday will be mainly fine although clouds that develop in the afternoon may lead to isolated showers in the mountains and inland.
Temperatures will rise to 41 C inland, around 32 C on the west coast, around 34 C on the remaining coasts and around 31 C in the mountains.
Tonight will be mainly fine. Locally there may low cloud or patchy fog, mainly on the coast. Temperatures will fall to 24 C inland, the south and east coasts, around 21 C on the remaining coasts and 19 C in the mountains.
Sunday, Monday and Tuesday will be mainly fine but clouds that develop in the afternoon may lead to scattered showers or thunderstorms in the mountains and inland.
Temperatures are expected to remain at the same levels, which are above average for the time of year, mainly inland and in the mountains.