For couples who share a bed it can be a constant source of sleepless nights - not to mention arguments.
No sooner is one beginning to drift off than the other starts tossing and turning because they are too hot or cold.
Now, scientists say they have found a way to keep the peace in the Land of Nod - and believe the secret is all in the duvet.
It seems wool-filled covers act in an "intelligent" way that helps regulate temperature more efficiently than feather, down or polyester fibre-based bedding.
Night overheating is often caused by moisture from perspiration, which traps heat and causes a cycle of further sweating and temperature rises.
But University of Leeds studies proved that wool fibres, based on the protein keratin in hair, nails and skin, can hold up to a third of their own weight in moisture before feeling damp. They draw heat and moisture away from bodies, helping maintain a comfortable temperature.
READ MORE: • Wearing underwear to bed is bad for your health
People produce heat and sweat at different rates, but wool can control the microclimate around each body. It means heat will be drawn away from the overheating sleeper but not from the cooler partner.
The study compared wadding from different types of duvet sold in the UK. It analysed how they cooled down from an extreme 70C temperature (158F) and how they performed in ideal 17C (63F) conditions.
In tests, wool allowed 67 per cent more moisture to escape over an eight-hour period than feather/down wadding, and 43 per cent more than polyester.
Wool could cope with nearly double the amount of perspiration per hour than feather/down and around 50 per cent more than polyester.
It was able to maintain the optimum sleeping body temperature of 35.1C for the longest, while feather/down and polyester instead caused it to exceed 36.1C.
Chris Tattersall of The Wool Room, which commissioned the study, said: "We've always known the benefits of wool.
"However it's great that we now have pioneering research evidence to support this."