Portugal has an average of 300 days of sun per year, so if you would have to define the Portuguese weather in one word, definitely, it would be sunny. Its geographic location allows Portugal to enjoy hot and long summers and the winter temperatures are usually mild. In the Summer, the temperatures go usually until 32º and, on the winters, 10º is already what we can consider a cold temperature. However there are obviously exceptions where the temperatures can go slightly above or lower, specially in inland hilly areas.
As for walking tours in Portugal, the ideal conditions are mild temperatures, not too hot or cold, so the best months are March, April and May (however this last one might surprise you already with high temperature) and then during the months of late September, October and November. However if you are not very temperature sensitive, you can go ahead and book your walking tour almost all year long, just exclude the months of July and August because of the hotter temperatures, since the winter temperatures for most Europeans are very reasonable.
Another good trick to plan you walking tour in Portugal is to adequate the destinations you visit to the different times of the year. If you would like to have a walking tour in the Algarve, the warmest region of the country, then plan your trip closer to the winter times as well as if you would like to have a coastal trip along the Alentejo or even in the inland area. If you would like to visit the centre of Portugal, including our biggest mountain range called Serra da Estrela, then avoid the months closer to the winter as this is the region that gets lower temperatures together with the very north of the country. Well if the Douro region and its vineyards landscapes are you preferred destination, then select the month of October, where you will still appreciate the harvest season, or then in the Spring, where the almond trees colours the region in white.
Portugal is a country of mild temperatures so our invitation is for you to come along in the Spring and then again in Autumn, since the colours of the landscape change dramatically!