What tog duvet for summer? Here is what you need to know.
4.5 tog is the one. Light enough to stop you overheating, substantial enough that you're not just sleeping under a sheet. It's the standard summer duvet for a reason.
If you run particularly warm, the all seasons duvet splits into a 4.5 tog layer you can use on its own (which means you're also getting more use out of something you already own).
Anything above 10.5 tog is winter territory. If that's what's currently on your bed, that's worth addressing!