I had been planning to write about Big Coats today. The optimum length and chic silhouette, most useful colour and smartest fabrics – all that stuff. A Big Coat is a big decision, after all. But I’ve changed my mind. The big debates about the Big Coat can wait until next month. I’m not doing this to be annoying, but rather (I hope) to be useful. Hold your horses, my friends. To every thing there is a season, and the time for the Big Coat has not yet arrived.

The Big Coat gets a lot of fanfare from about mid-August onwards. It takes up a disproportionate amount of space, in every sense, because the slice of winter that is absolutely freezing is much smaller (most years) than the seasons either side, when it is chilly rather than Baltic. In the shoulder seasons, the Big Coat feels seductive first thing in the morning, when both the mercury and your psychological defences are down. But by mid-morning you will be either gently sweating, or lugging it around over your arm. Neither of these looks is chic.

It will probably snow solidly for two months now just to make me look like an idiot. But the point still stands, because the climate emergency makes a mockery of the schedules we devised for our wardrobes decades ago. Long, mild shoulder seasons have been a feature of many recent winters.

A great transitional coat will see you up until party season – when looking for a taxi late at night requires a Big Coat – and if we are lucky it will be back in the game by March.

First, hemline: this will sit no higher than the hipbone, but no lower than mid-thigh. Waist length is too draughty, but anything longer than mid-thigh creates too much overall weight. Second, fabric: if a breeze blows on the outside, you don’t want to feel it on the inside. So we are not talking about a fine wool blazer (although show me a sturdy jumbo-cord blazer, fully lined, and we can talk) and not a big cardigan, which is cosy for padding about the house but next to useless on a windy pavement. And the neckline needs to be high enough to keep your breastbone under wraps. You want to keep your core toasty, but allow enough air for the rest of you not to get overheated.

I am in the market for a new transitional coat this season because my go-to for the past four years is now looking decidedly threadbare, so I thought you might be interested in what my research has turned up. I am very taken with Phase Eight’s Nicci coat, currently reduced to £125, which has nice wide lapels and a tie belt. A belt is a bonus on a transitional coat, adding both snuggle and a topnote of polish, like tying a ribbon round a gift.

The Mathias Coat by French brand Sézane is delicious, with a deliberately floppy collar that you can turn in or out. The responsibly sourced wool is strokably soft, the café-au-lait colour very chic. No belt, but double-breasted, which makes it cosy, and would work with tailored wide-leg trousers for an office day, or with your favourite jeans and a sweater for an outdoorsy Saturday. It is £295, but like many of us I don’t buy many new clothes these days, and the pieces I have bought from Sézane have all turned out to be wardrobe treasures, looking if anything nicer IRL than on the hot French chicks on the website, which is frankly a miracle.

Last but not least, John Lewis has a cuddly Teddy Jacket for £99, in black or toffee. From now till next summer is a marathon, not a sprint. And bigger doesn’t always mean better.

Hair and makeup: Sophie Higginson using Kiehl’s and Nars. Model: Sherin at Body London. Coat and boots: both Boden. Earrings: Alighieri. Skirt: Zara.