Days when you need to make a good impression can fall in every month of the year. Handily, suits come in light, mid and heavy fabric weights, so you can feel confident without shivering in winter or mopping your brow in summer.

But just looking at the fabric won’t tell you how warm or cool a suit is – there are summer-weight tweeds, after all. So here’s the lowdown on how to how to find out whether a suit will be a winter warmer or light and breezy for summer.

FIBRE VS WEAVE

Some fibres are naturally heavier than others. You’d expect a linen suit or Tencel shirt to be lighter, for example. But when it comes to wool, the weight is more technical as it depends on the thickness of its fibres and tightness of its weave.

When you’re shopping for a suit, you may notice some mentions of GSM. This figure is the weight per square metre, and it’s how you figure out if the suit is lightweight or heavyweight.

So what numbers should you look out for?

HEAVYWEIGHT SUITS

These suits are cut from cloths that weigh upwards of 400GSM (or 14oz as they may also be called). Think traditional tweeds and Donegal weaves, as well as those used for coats.

They’re ideal for winter because they let shut out the cold air to keep you warm. Tailors also love using heavy fabrics because they give more structure and drape beautifully to tease out wrinkles. That’s why heavier cloths are generally more formal.

LIGHTWEIGHT SUITS

Any suit cut from a cloth below 270GSM (or under 9oz) will be very lightweight. The looser weave allows plenty of airflow to keep body temperature down. If you want to wear a heritage-look tweed or herringbone suit in summer, there’s no reason why you can’t if you choose one in a light weight.

We’ve cut the grams even more with our lightweight suits by removing the shoulder padding and choosing minimal lining.

SOMEWHERE IN BETWEEN

For an all-rounder, a midweight suit should do a bit of both. Cloths weighing between 290GSM and 390GSM are usually wearable for most of the year.

If you’re just getting started with your suit collection, go for one that’s 290-360GSM for an all-season outfit and expand your options from there. Look for half-lined jackets for a smooth fit on the arms and more breathability on the back or opt for a lined suit if you want something that bit warmer.