Tent Condensation: Why You Wake Up Wet and How to Stop It

It's a fall morning, the sky is clear, it never rained, and the inside of your tent is wet. The walls drip on your sleeping bag when you sit up. Most people assume the tent leaks. It almost never does. That water came from you.

01Where the water comes from

You breathe out moisture all night, and your body gives off more through your skin. Add a second person, a wet dog, damp clothes and boots inside, and that's a lot of water vapor in a small space.

As the night cools down, the tent walls and rainfly get cold. When the warm, damp air inside hits that cold fabric, the moisture turns back into water, the same way a cold glass of iced tea "sweats" on a summer day. Fall nights are the worst for this: the air is often damp, and the temperature drops a lot between evening and dawn.

02How to cut it down

1. Open the vents. This is the big one. Most tents have vents up high in the rainfly. Open them, even when it's cold. Closing everything to stay warm traps all that moisture inside. Your sleeping bag keeps you warm; the tent's job is to keep the rain off.

2. Stake the rainfly tight and away from the tent. The gap between the tent body and the fly lets air move. A fly sagging against the tent body soaks through where it touches.

3. Crack a door. If it's not raining or windy, leave the top of a rainfly door unzipped a few inches on the side away from the wind.

4. Keep wet stuff out. Wet jackets, boots and towels go in the vestibule or the car, not inside with you. Don't cook inside the tent (it's a carbon monoxide and fire danger too).

5. Pick your spot. Low spots, right next to a lake or creek, and open meadows collect cold, damp air. A spot under trees or a little higher up usually stays drier.

03When it happens anyway

• Wipe the walls in the morning with a small camp towel or sponge.
• Keep your sleeping bag from touching the tent walls.
• Dry everything out before you pack up, or as soon as you get home. Packing a wet tent away leads to mildew.

04What about tent heaters?

Some heaters make the problem worse. Burning propane makes water vapor along with heat. If you use a heater, use one made for indoor use, follow the directions and keep ventilation open. See tent heaters: what's safe and what isn't.

Photo by bhossfeld on Pixabay.

Related: Fall Camping: How to Stay Warm When Nights Drop Below 40 · How Much Water to Haul When the Spigot Is Off