The Barcelona Weather is very mild compared to Northern Europe, slightly cooler summers than here on the Costa Del Sol where I am, but with slightly colder winter temperatures.
Still the rule for the weather in Barcelona still apply, the best months for visiting are May, June and September, wonderful temperatures, clear, blue skies but not that overpowering, humid heat!
Items To Pack
If you are coming here for a break between September to May bring a jacket and jumper for the nights and just in case there are some cold days. In the real winter months, November, December, January & February bring a coat etc.
The other thing to bring in the winter is slippers, if where you are staying has Limestone or marble floors your feet will freeze!
Pack lightweight clothes for the summer months.
Is the weather in Barcelona hot enough to sunbathe all year?
Sunbathing is not really possible all year round, especially between October and May when you can get quite cold winds. However if its sunny, its warm enough to sit outside, at least for 2 hours per day for eating al fresco or just enjoying the sun and Barcelona Weather over a coffee.
You can get a tan virtually everyday from June to the beginning of October.
Choosing a Car
Get a car with Air-conditioning from April until October, take a view on it from November until February. Even though you are unlikely to use the Air con much in the winter months the weather in Barcelona can throw out the odd Hot day during the winter.