The met office has issued a yellow weather warning on for Wednesday, in effect from 11am to 5pm.
Temperatures inland are set to rise to 40C, the met office said. On the western coast temperatures are expected to reach 32C, while on the rest of the coastal areas, the temperatures will reach 33C.
In the mountains the temperature is expected to reach 30C.
The public is urged to be careful, especially vulnerable groups, including elderly individuals and small children.