Porto has a Mediterranean climate with dry warm summers and mild winters. Over the course of a year, the temperature typically varies from 6°C to 24°C and is rarely below 2°C or above 30°C.
Although the weather in Porto becomes unpredictable during the spring months (Mar-Jun) it is warm and comfortable. During the season the average high increases gradually; 16°C in March, 18°C in April and 20°C in the last month of the season. The city receives more hours of sunshine as the season progresses.
You can find more information about the climate in Porto in www.infoporto.pt.