I asked an M&S sleep expert when the best time is to switch to a winter duvet – this is the exact date to make the change if you don't want to ruin your sleep

Wondering when to switch your summer or autumn duvet for a warmer winter option? Me too, which is why I spoke to sleep experts at M&S to find out a definitive answer.

After all, in Britain, where temperatures fluctuate dramatically throughout the year, even the very best duvet is unlikely to see you through all twelve months of the year without needing to be swapped out for something warmer (or cooler) with the change in season.

As it turns out, M&S's sleep experts have calculated the *exact* date you should make the swap to a winter duvet if you don't want to disrupt your sleep. And that date is coming up soon...

As Melissa Goldman, senior buyer at M&S, explains, 'as a general rule of thumb, we recommend changing your duvet in line with outside temperatures to ensure optimal sleep quality.' That means that as outside temperatures drop, your duvet tog should go up in order to keep you at a comfortable temperature during the night.

However, beyond this general advice, the experts at M&S have gone one step further and analysed weather data from 2025 to reveal the exact date people in the UK should consider changing their duvet in 2026.

So when is the big day? 'For winter, the 7th November is the date to change your duvet,' reveals Melissa. 'Temperatures dropped below 15°C on this date in 2025 and remained there or below until year-end, making this the perfect time to switch to a warmer winter duvet.'

Good to know. But what exactly does 'warmer' mean, and what happens if weather patterns this year don't follow last year's patterns? Well, luckily M&S has put together a handy cheatsheet to help you gauge when to swap your duvet, as well as what to swap it for.

The above chart shows the ideal duvet tog rating for the outside temperature. But you might be wondering what duvet tog actually means. 'A tog (thermal overall rating) measures the thermal insulation of bedding,' explains Melissa. 'The higher the number, the better the duvet will retain heat and keep you warm.'

'The lightest duvets (anything below a 4.5 tog rating) are best suited to the summer months when temperatures frequently exceed 18°C,' explains Melissa. 'Duvets ranging between a 7.5 and 10.5 tog rating are best for transitional seasons like spring and autumn, and 10.5 tog duvets are ideal for winter.'

That said, 'while a 10.5 tog duvet is sufficient for most modern homes with central heating, for those who feel the cold especially at night, a 13.5 tog duvet is a good option for the coldest winter months,' advises Melissa.

And of course, as Hannah Shore, head of sleep science at MattressOnline, points out, 'the perfect temperature will be slightly different for everyone.'

After all, 'just as you will see some people walking around in shorts and T-shirts while others are in jeans and a hoodie and still cold, the same happens while you sleep,' says Hannah. 'You may have some people who are naturally cold when they sleep and some who are naturally warmer.'

However, like Melissa, Hannah agrees that 'a rough rule of thumb would be 7.5 tog duvets and below for warmer months, and 10.5 tog duvets and above for cooler months, with the larger the tog, the warmer you will feel.'

And as well as getting the right tog duvet for the season, Hannah is also keen to stress just how important listening to your body is when it comes to choosing your winter bedding.

'Our core body temperature needs to drop by a couple of degrees to get access to the good quality sleep we need,' explains Hannah. 'If our environmental temperature is too hot, our core body temperature will struggle to drop, leaving you struggling to fall asleep, waking frequently throughout the night, and feeling rubbish the following day.'

On the flip side, 'if our environmental temperature is too cold, your body is concentrating on trying to warm you up,' says Hannah, and that's a surefire way to ruin a good night's sleep, too.

'We all need to find the right balance and our optimum temperature so we can have a perfect night’s sleep,' says Hannah, and that means paying attention to expert advice, but also factoring in our own preferences and circumstances.

As Hannah points out, that means things such as 'your personal body temperature, how you respond to changes in temperature, how many people are in the bed, whether you have fans or air conditioning, and whether you sleep with a partner, children or pets.'

Get the balance right, and a deep and restful night's sleep is much more likely to follow.