From bold tones to breezy linen neutrals – here’s how to look cool in a blazer, even when it’s hot.

Summer, traditionally speaking, is not an easy time for the man who needs to dress with a touch of formality. The traditional wool jacket, the tie, the strangulating shirt seem to have been created specifically as a means of torture. Or so it used to be.

Today, a man putting on a jacket in summer, out of choice or necessity, has many more options combining comfort with style. The best of them achieve this by using a lightweight, breathable fabric and a casual, unstructured style. Do bear in mind that breathability is just as dependent on the way a fabric’s woven as it is on what the fabric itself. Tightly woven linen will feel much warmer than wool designed to let the breeze through, so read the product descriptions closely.

This summer, the style-setters are wearing T-shirts, polo shirts and camp-collar shirts under their jackets. Read on to find out how the best-dressed guests at June’s Pitti Uomo fashion fair in Florence made summer blazers work for them.

This fellow’s outfit is truly popping, thanks to the intensity of his blue suit, which looks very close in colour to International Klein Blue, a shade first mixed up by the mid-20th century French artist Mr Yves Klein. The colour’s impact is due to the heavy use of ultramarine in the blend, and it has an intensity that’s hard to tear yourself from. Despite taking the form of a two-piece suit, the trousers and jacket are themselves soft and casual. They seem to take their inspiration from old French workers’ jackets. This unlined blazer will feel cool to wear and looks comfortable, while the monochrome suit does nothing to distract from the wild, tiger-inspired shirt worn beneath. How wise of this man to keep his shoes and socks so simple, rather than wearing a showier combination that could have tipped the outfit over the edge.

Nothing speaks of summer like earth tones, which work best when worn in powerful sunlight and against tanned or dark skin. The man on the left has a casual-looking suit in dark olive cotton, which he’s wearing over a fully fashioned polo shirt. Note the way the placket and the collar differ from those on regular piqué polo shirts. The overall effect is relaxed, even though he’s wearing a suit. His companion on our right, however, makes a different impression. He looks much more dapper, even though he’s wearing khakis and a blazer. The reason is that the jacket breaks the mould with eye-catching gold-coloured buttons and shawl lapels more normally seen on smoking jackets. These days, any tie is attention-grabbing, but particularly in this case because it’s got such a large print. The loose-fitting linen trousers dial down the impact and balance the overall effect.

The navy blazer comes in many forms and if a traditional blue one seems a bit fusty these days, a casual version of the classic nautical style still feels relevant. The navy cotton jacket on the left retains the double-breasted form, the peak lapels and the brass buttons typical of a classic blazer, but is transformed by the cotton fabric, its short length, the lack of any structure and the T-shirt worn underneath. The slim, cream-coloured trousers contrast well with the dark jacket and the pocket square strikes a dapper note without seeming intrusive. Meanwhile, the man in the background is in a similarly neat-fitting jacket, but this time it’s single-breasted and has a window-pane check. His biscuit-coloured chinos are a good choice and connect the outfit to the world of workwear. We also like the vintage-looking sunglasses both men are wearing.

More earth tones, this time in mismatching stone shades as the jacket and the waistcoat are not a pair. Not that it matters because the result is more casual and, dare we say it, has more sprezzatura than a matching jacket and waistcoat would have been. Talking of sprezzy, have you noticed the jacket’s last cuff button is artfully left undone to telegraph the fact that the buttonholes work and hint that it might be bespoke? The patch pockets are another casual touch (not that anyone but tailoring nerds ever notice them), and help to explain why the jacket looks so right over a T-shirt. Not every blazer looks natural when worn over a T-shirt, but this one works because it’s innately casual. The olive-coloured trousers, which are looser than the ones most guys were wearing even a year ago, allow the air to circulate and exude a sense of comfort. We also like the turquoise and silver ring. This man has style to spare.

This pair of bearded Spaniards are Mr Carlos Castillo, on the right, and Mr Jorge Navares, on the left, the two guys behind the casual-tailoring brand Man 1924. They are world-class exponents of the casual but trad look, and this shot perfectly captures their easy style. Mr Navares seems sporty in his New Balance sneakers and drawstring chinos, even though he’s also wearing a checked linen sports jacket. He looks entirely relaxed about the rumpled linen, as he should. Wrinkling is part of linen’s charm and must be embraced by anyone who wears it. Mr Castillo is also wearing a casual-looking jacket, in earth tones with a houndstooth pattern. Both men are in navy blue polo shirts and loose-fitting cuffed trousers, and both seem enviably at their ease.

A brown suit is a sophisticated choice. It appears to be made from a version of seersucker, the fabric that’s woven with permanent wrinkles so it never lies flat against the skin and allows for good air circulation. In this case, the darker stripes are generously sized, which makes them pretty striking. Other than the fabric, it’s a largely classic jacket with a generous notch lapel, horn buttons and patch pockets, and the comfortable look extends to the matching pleated trousers. The wearer has wisely chosen to wear a simple white T-shirt underneath his jacket, which contrasts nicely and does nothing to draw our attention away from the suit. Overall, it’s a bold outfit, but in our view a successful one.

The difference in the impression made by printed T-shirts and plain ones is huge, as this man demonstrates with a tee that looks radically more casual than an unadorned version would. It’s worn over a simple-looking, subtly checked navy blazer that’s understated and versatile (yes, it’s got patch pockets) and a pair of azure cotton chinos that strike a jaunty note (and which we can easily imagine worn with a pair of espadrilles by a hotel pool). The retro running shoes sit harmoniously with the rest of the outfit. Any kind of leather shoes, except perhaps deck shoes, would have been too smart to work with that T-shirt.

The people featured in this story are not associated with and do not endorse MR PORTER or the products shown