It should be quite sunny and hot, there may be some showers but I don't think it will be overcast for too long.
I would tend to wear smart casual, and take a jacket, and layers. May be a pashmina. I would also take an umbrella and a waterproof with a hood. I would also take some trainers, as there may be an opportunity for walking. I really enjoyed walking as you can take a cable car to the mountain top and then walk along closely cropped well sign posted grass paths.
I hope you have a lovely time.