Most save the date cards will not require more than a typical forever stamp (first class) when you are mailing with the US postal service, because they are usually fairly small (5x3.5 inches, 5.5x4.25 inches) and will weigh under an ounce.
Day by Day weather log for Barcelona Weather in September. September 30. Daily Comment: Temperature 25Â° C around 77 F Warm and sunny light cloud at times but generally clear skies. Day 29. Daily Comment: Temperature 25Â° C around 77 F warm and sunny. A little light cloud at times from 15:00 onwards.
However, Barcelona doesn't tend to get quite as hot as Madrid and the temperatures here won't as fierce as they tend to be in the capital. The average maximum temperature in Barcelona in September is 79Â°F/26Â°C and the average minimum temperature is 63Â°F/17Â°C.