Average Temperatures in Barcelona, Spain. 1  The annual mean temperature in Barcelona, Spain is very mild at 15.3 degrees Celsius (59.6 degrees Fahrenheit). 2  Mean monthly temperatures vary by 14.2 C (25.6 F) which is a low range.3  The variation/ range of daily mean temperatures is 6.7 C (12 F). The annual mean temperature in Barcelona, Spain is very mild at 15.3 degrees Celsius (59.6 degrees Fahrenheit). 2  Mean monthly temperatures vary by 14.2 C (25.6 F) which is a low range.