The Belgian Met Office RMI has extended its Code Yellow heat warning until Saturday.
Previously, the warning was only in force until Friday. The warning applies to the whole country. On the coast, Code Yellow will not come into effect until Thursday.
Temperatures of 30 degrees and above are forecast across the country for almost the entire week.
Under a Code Yellow warning, the RMI advises people to remain vigilant. Measures may also be taken to protect the elderly and vulnerable people, for example by ensuring they drink enough fluids and avoid prolonged exposure to direct sunlight.