Why an air mattress sinks overnight
An air mattress is a sealed, flexible chamber, not a rigid platform. The air inside pushes outward against its fabric, and that tension supports a sleeper. If air escapes through a tiny puncture, a seam, or a valve that is not fully closed, the mattress loses pressure. Its surface then bends farther under the same weight, so the change can feel gradual: first softer, then noticeably lower.
A mattress can also feel less firm as the night cools. Cooler air takes up less space, lowering pressure inside the mattress even when no air has escaped. That effect usually follows the temperature change; a leak tends to keep worsening. A valve check and a quick inspection for damage can help distinguish the two.
Why the ground feels colder as it deflates
At a campsite, the ground can draw heat from a sleeper. An air mattress helps separate the body from the earth, but it is not necessarily a warm layer: air inside can circulate and carry heat away, and the mattress’s insulation varies by design. As the mattress collapses, the sleeper gets closer to the ground and may press through the remaining air space. That makes a leak a comfort problem and, on a cold night, a more consequential one.
Before bed, close the valve firmly and check that the mattress holds its shape under weight. If it softens overnight, reinflating may restore height temporarily, but it will not stop the leak. A small repair kit can turn a night of repeated sinking into a manageable fix—especially when the alternative is waking with the ground only a thin layer of fabric away.
