The Algarve has many days of unbroken sunshine with high temperatures. These are cooled with the breeze from the Atlantic making the temperature a little more comfortable. Between the months of June and September, there is little or no rainfall.
Spring & Autumn
The weather for May & October in Portugal is better than the summer in the UK. A little rain or a few cloudy days are possible, and evening temperatures are lower than in the summer months.
Winter
The Algarve does not tend to see prolonged periods of miserable weather. It does rain and downpours are heavy when they occur, but they clear up quickly and happen a lot less often than in the UK.