Olhao: Weather Forecast. The warmest day over the next 7 days in Olhao is forecast to be 25th April at 23°C (73°F) and the warmest night on 21st April at 16°C (61°F). The average temperature over the next 7 days is forecast to be 22°C (72°F) and there will be 6 days of sunshine . The average for April is 17°C (62°F) in Olhao. The warmest day over the next 25 days in Olhao is forecast to be 3rd May at 24°C (75°F) and the warmest night on 21st April at 16°C (61°F). The average temperature over the next 25 days is forecast to be 21°C (70°F) and there will be 17 days of sunshine .