The weather in Portugal in June and July should be perfect for relaxing on the beach, and is ideal for your trip to the Douro River. The conditions will be hot with temperatures above 26 degrees Centigrade in most parts of the country .
Average maximum temperatures are 25 degrees Centigrade in Porto and 28 degrees Centigrade in the Algarve, though daytime temperatures usually rise to above 30 degrees Centigrade.
Rainfall is usually at a minimum except for the occasional shower in the north. As a whole the country enjoys cooling breezes from the Atlantic.
Theres actually a really helpful
Weather page that you can keep an eye on leading up to your journey. Hope you have a great time.