Now I checked where is Costa Da Caparica :) such a nice place, I imagine you have been there when the weather was nice. Though spending time on the beach during the winter can be nice too, if there is no seastorm or similar :D
We had so much luck with the weather as it was the beginning of January when we did this road trip. Actually, we heard that it was rainy but that we brought sun and nice weather with us :)) Three fully sunny and bright days in Lisbon, that was so good. I had plenty of time for exploring and seeing stickers hahaha. Then we went to the north. Last day - Porto, the weather changed radically... very heavy rains chased us away from there, and we literally dragged a cloud of rain behind our car 😂