what to wear for son's graduation

[NetZeroZealot]

It's next week, in Scotland. Forecast is cold & wet.
The Ghost floral summer dress I'd planned on wearing won't be appropriate.
What should I wear instead?

Nice trousers, top and jacket? Do you know how much will be indoors and oitdoors?

Ceremony itself is in a hall. So inside. Just outside for nice photos.
Am also thinking trousers & jacket, but everything I've got like that is a bit corporate feeling.
Except wide leg jeans which feels too casual ...

Usually air conditioning in the ceremony halls so make sure you are warm.