The Algarve probably has the best climate in Europe for anyone looking for warmth and sun on their surf trip. With 300 days of sun a year, the Algarve summers start mid May, and end mid October. May, June, September and October are often warm enough to wear shorts.
Even in the winter months, you will find yourself in a t-shirt on a terrace in the sun with an ice-cold beer after your winter surf on the south coast, at beaches like Porto do Mos, Meia Praia, Zavial, Burgau, praia da rocha, and more. Out of the high season is a perfect time to get away with your friends or family as the flights are cheap, the sun is out and the waves are great.
With 300 days of sun per year, and average of 3000 sun hours per year, the Algarve is definitely a sunshine paradise. In summer, the Algarve has an average of 12 hours of sun per day. This decreases to 6 ot 7 hours per day in fall/wintertime, also because the days are shorter in this period. Any time of year you'll love the sunny hours in the Algarve.
The temperatures in the Algarve are very comfortable, with spring averaging around 20 degrees, summer around 27 degrees, fall around 22 degrees and winter around 15 degrees during the day. Nighttime temperatures in summer stay around 20 degrees, making it a perfect environment for late night dinners out in town, beach sessions and garden dinner parties. In winter, nighttime temperature drops to around 10 degrees, but it doesn't ever freeze, explaining the palm trees that line every boulevard in the Algarve.
The Algarve has very comfortable humidity levels, especially in summer, with averaging humidity levels of 60 - 65%. In winter the humidity levels can get up to 85%, but with the sun out during the day it still is a very moderate and enjoyable climate for a surf and a terrace-beer after.
If you like your summers to be rain-free, the Algarve is definitely the right pace to be. The average rainfall in the Algarve summer is 10mm per month, which is next to nothing. Rain in spring averages 30mm per month and 50 mm per month in fall, which still comes down to only a short inconvenience for your holiday. November and December have the highest chance of rainfall, with an average of 100mm per month, but because it comes down in short periods of time, there won't be an ever-lasting drizzle ruining your entire holiday. Rather, you'd have to spend one rainy day in the water (you're wet anyway), and you can hang out in the sun the rest of your holiday.
All in all, the Algarve is an amazing destination when it comes to the weather.