The ideal tog rating for a winter duvet depends on personal preferences and environmental factors such as the temperature of the bedroom and the season. Typically, duvets with a tog rating over 10 are ideal for winter, but lower ones may be suitable for sleepers who get hot at night. A 13.5 tog winter duvet is perfect for the colder months, depending on how low the temperature drops in the bedroom overnight. However, it is important to consider that a thicker duvet may not necessarily offer more warmth, as a thinner one made from better insulating materials might actually do a better job. It is also recommended to invest in two different duvets, one for summer and one for winter, to keep cool on warm nights and snug and toasty when the temperature drops.