A summer wardrobe doesn't always mean seersucker or linen. There are plenty of other ways to add a touch of summer to your outfit.
A navy hopsack blazer is a great place to start. It's breathable and looks sharp. Plus, it's more versatile than a casual linen jacket, which would look out of place in more formal settings.
For trousers, tropical wool is with an open weave is a must. The last thing you want is for your trousers to cling to your sweaty legs like Saran Wrap. If you favor grey, switching to a lighter shade is another way to make your outfit more cheery.
Lastly, don't be afraid to introduce new textures. A raw silk tie and suede shoes can add some visual depth to an outfit consisting of solid patterns.