Like the inside of your nose, but all over your tent.
Here's what the National Park Service thinks: "The condensation of water vapor into clouds and precipitation is a vital link in the water cycle."
Picture throngs of gorgeous buzzing neon rainbows at sunset while butterflies flutter by gently and birds sing their last glorious notes of the day in perfect harmony among amazing, delicately-leafed trees, and the skin of your weenie puffs out as it roasts over a crackling fire.
Meanwhile, next morning, in his tent on an actual trail, so far from civilization that he can't see a parking lot or even hear traffic anymore, in a place where animals snuffle and snort around without proper supervision and eat each other when they meet, Harold Hiker awakes from sleep.
Harold has been hiking in the rain that fell from the Park Service's condensation. Harold knows what condensation really means. Most of the rain that was aimed at him hit the ground and bounced, and then ran straight into Harold's boots, and then climbed up his legs and really got to work.
When Harold set up camp he did it with a great sigh of relief. At least, at last, he thought — at last he could stop walking and get some relief from the damn rain. For a few hours anyway he would be someplace dry where the rain wouldn't be jackhammering his head and slithering up his legs in pursuit of his underwear.
Harold wanted a night of rest. He got out of his wet clothes and right into his sleeping bag and gratefully fell asleep. When Harold woke the next morning he found that the entire inside of his tent was full of condensation.
Condensation above him, condensation below him, condensation on every side of him. His sleeping bag was soaked with it. And now it was closing in for the kill. Condensation has no conscience or sense of humor, you see. Condensation will not mellow out and just be your pal. Condensation is dedicated to doing you in.
Condensation is the physical process that changes a gas to a liquid, and liquid is the stuff that makes you wet.
This is the mad dog of physics that was in the tent with Harold, and Harold had nowhere to go. Poor Harold. Some say that double-wall tents are a bad deal because they don't allow enough air circulation to prevent condensation. This may be true, but you haven't been to hell until you have spent the night closed up tight in a shiny-new single-wall tent.
Some say that tarps are better than either of the above because tarps allow more air circulation and thereby defeat condensation buildup.
This may be true, but you haven't been to hell until you have spent the night under (under is used loosely here) an open tarp, exposed to exactly every single puff of freezing, incessantly probing, rain-saturated air in the known and unknown universes.
In other words condensation is an immutable force of nature that will always be with us. Like every other form of liquid water and all known immutable forces of nature, condensation slithers and creeps around, over, into, and through everything, anything, and usually the place it wants to go most is the very last place you want ever to find it.
Nasty. It is nasty. That is the only way to say it.
The only sure way to avoid condensation is to stay home and watch TV with a big bowl of chips and a few beers handy, in front of a hot fire.
You can roast your weenie in comfort there. Dry, condensation-free roasting, in comfort, of your weenie.
And you can have pets there too. Which are also warm and dry and soft and fuzzy. Unless you are into lizards.