Memory Foam and Temperature
Memory foam was originally designed to be very energy absorbent. This means that on a particularly hot night, your mattress will be absorbing the heat around it as well as your body heat. Traditional memory foam mattresses are relatively dense, leaving little room for airflow within the mattress itself.
In addition, because memory foam is made up of a synthetic and non-breathable material, the heat that is absorbed builds up in the mattress, and then is directed right back at you, instead of simply being dissipated. In fact, the memory foam material actually uses your body heat to contour your body and mold itself to your particular shape.
As a result, the longer you sleep on it and the hotter the environment, the hotter the mattress will feel. This is why memory foam mattresses may feel like they get progressively hotter as the night goes on. If you sleep with a partner, your problem can get doubly worse, because now you’re dealing with two warm bodies heating up that energy absorbent mattress.
Add all this up, and you’ve got a potential for some sleepless nights on memory foam, especially if you prefer to sleep at a cooler temperature.