Summer weather lasts from June well into mid-September. It is very sunny and dry. July and August can get very hot in the centre and south of the country. But northern areas remain cooler. So if you’d like to avoid the heat, visit Porto, where the daily average temperature in July is around 20 °C. Swimming season on the northern coast starts only in mid-August and lasts until mid-September, as water always remains rather cool.
The southern coast is the warmest which makes it perfect for beach vacations. Swimming becomes comfortable from mid-July. Due to the ocean breeze, the heat is not an issue. While at south-central plains and valleys at low latitudes it can become intolerable due to hot winds from Africa, which bring extremely high temperature.