British weather in August, begging for dressing guidance

I went to school in Edinburgh~ I can tell you that in Edinburgh (in fact, most of the UK) there is basically no difference between spring, summer and autumn. It’s just that it will be warmer for a few days in summer. If you wear short sleeves, it will definitely be cold. In summer, long-sleeved jackets are more likely to appear than short-sleeved tall jackets.

Of course, if you definitely want to wear short-sleeved jackets, make the jacket thicker