Waterproof your pack and gear
A wet sleeping bag or dead phone can turn a rainy trip miserable — or unsafe. The good news: keeping gear dry is cheap and simple once you stop trusting the pack itself. Here's the system that keeps the things that matter dry, no matter how hard it rains.
In plain English
A backpack is a bit like a tent with zippers everywhere. Even if the cloth itself keeps water out, rain finds its way in through the stitching, the zips and the gap at the top where your back meets the pack. So the smart plan is to keep what is inside dry, not to trust the bag.
The easiest way is a big waterproof bag inside the backpack, like a bin liner in a trash can. Put your sleeping bag, spare clothes and phone inside it. Small waterproof bags inside that add a second layer for the things that matter most.
Gear that gets wet has to dry properly afterward. Hang it somewhere airy and shaded rather than in hot sun or a clothes dryer, because heat and strong sunlight can damage the coatings that make fabric shed water.
The short answer
Assume your pack will get wet inside, and protect the contents from within: line the whole pack with a waterproof bag, and seal the things that must stay dry — sleep system, spare insulation, electronics and first aid — in their own dry bags. A rain cover is a nice extra, but the liner is what actually saves your trip.
Your pack is not waterproof
Even a "waterproof" fabric leaks at the seams and zippers, and ordinary pack fabric eventually soaks through in sustained rain. Water also runs down your rain jacket and your back straight into the top of the pack. So the real strategy isn't waterproofing the pack — it's waterproofing what's inside it.
A dry interior does double duty: it keeps your warmth (dry layers and sleeping bag) and your safety kit (electronics, first aid, fire) working when the weather is at its worst — the exact moment you need them.
Pack liner vs. rain cover
These two approaches are often pitched against each other; in truth they solve different problems, and a liner is the one to trust.
- Pack liner (inside): a big waterproof bag — a purpose-made liner, a heavy-duty trash-compactor bag, or a roll-top — that lines the main compartment. Everything goes inside it and stays dry even if the pack is soaked through.
- Rain cover (outside): a fitted cover that sheds light rain and keeps the pack cleaner. Useful, but it can blow off in wind, ride up, and does nothing about water running down your back.
- Best of both: use a liner as your real defense and add a cover on top when it's really coming down.
Dry bags for the essentials
Inside the liner, a few dry bags add a second line of defense and keep things organized. You don't need many — one or two for the truly critical items is plenty for most day and weekend trips.
- Roll-top dry bags seal reliably and come in sizes from phone-pocket to sleeping-bag.
- Zip-lock freezer bags are a cheap, light way to protect a phone, maps, permits and first-aid items.
- A dedicated waterproof stuff sack for the sleeping bag is worth its tiny weight on any overnight.
What must stay dry
Not everything needs protecting — your tent body and rain shell are meant to get wet. Focus your dry bags on the gear that keeps you warm, safe and able to call for help.
- Sleep system first: a wet down sleeping bag can be dangerous; protect it above all else.
- Spare insulation: the dry warm layer you put on at camp or in an emergency is useless if it's soaked.
- Electronics, fire and first aid: phone, headlamp, power bank, lighter/matches and your first-aid kit belong in a sealed bag.
- Food: keep it dry and, in bear country, in the right storage — see our packing checklist.
Reproofing your rain gear
A rain jacket that "wets out" — soaks on the surface and feels clammy — usually isn't broken; its water-repellent finish (DWR) has worn off. You can often restore it at home.
- Wash it clean first with a technical wash (not regular detergent, which leaves a residue that attracts water). Dirt and body oils are what kill DWR.
- Reapply a DWR treatment — a wash-in or spray-on product — following the label.
- Follow the labels for drying. Some treatments and jackets call for gentle heat and others say to air-dry, so follow the treatment label and your jacket's care label. Packs are different: Gregory, ULA and REI say never to put a pack in a dryer, and Nikwax says to air-dry its pack treatment.
Drying out and care
Managing moisture doesn't stop at camp. Dry your gear whenever you get the chance so damp doesn't become mildew or a cold night.
- Air the tent, sleeping bag and damp layers in a breeze, ideally in shade, at breaks and before packing up; strong sun (UV) can degrade fabric and water repellency.
- Never store gear wet at home — mildew ruins fabrics and down; let everything dry fully first.
- Refresh dry bags and liners between trips; a pinhole leak defeats the whole system.
Waterproofing pairs naturally with knowing how to hike in the rain and how to repair a pack in the field — together they keep a wet trip fun instead of grim.
How waterproof ratings and water repellency work
Two different things keep fabric dry. The first is a waterproof coating or membrane, rated by hydrostatic head: the height of a column of water the fabric can hold back. If water breaks through at 1 meter, the rating is 1,000 mm, as Sea to Summit explains.1 MSR describes the test as pressing a column of water against the fabric until three drops pass through.2 Most pack fabrics have such a coating inside, but REI says water can still seep through seams and zippers.3 Deuter makes the same point about sustained downpours.4
The second is DWR, an invisible water-repellent finish on the outer fabric that makes water bead up and roll off.5 When DWR wears off, the face fabric soaks up water even if the coating behind it holds. Deuter's quick test is to drop water on the fabric: if it soaks in rather than beading, it is time to re-waterproof.4 Nikwax adds that normal laundry detergents leave a water-attracting residue on outdoor fabrics.5
Heat and reproofing: what the brands actually say
Some guides suggest activating a fresh treatment with gentle heat, such as a cool tumble dry or a warm iron. For packs and pack fabrics, the manufacturers in this site's library say the opposite. Nikwax's spray-on treatment for synthetic tents and packs is applied to clean, wet fabric from about 6 inches away, then air dried only and left to dry fully before use or storage.6 Gregory says not to machine wash packs or put them in a dryer, because it can damage protective coatings,7 ULA says never to use a dryer,8 and REI's general guidance is never to machine wash or machine dry a pack.9
Rain jackets are a separate case, and the library has no source on heat for jacket finishes. The safe rule is to follow the jacket's care label and the treatment's own label exactly, and never to put heat on a pack. For cleaning before treatment, Deuter recommends lukewarm water with a pH-neutral soap,4 while Gregory advises against detergents and solvents entirely.7
Why a dry kit is a safety issue
The CDC says hypothermia can develop above 40°F when a person is chilled by rain, sweat or cold water.10 NIOSH adds that wet feet lose heat 25 times faster than dry ones, and that trench foot can occur at temperatures as high as 60°F if feet stay wet.11 The Park Service warns that cotton absorbs water and stays wet a long time,12 while polyester fleece dries quickly and stays warm when damp.13 Keeping a spare layer and dry socks sealed away is what makes those facts manageable.
Drying location matters as well. REI says to dry packs in shade or indoors because UV light degrades fabric,9 and Nikwax says UV exposure destroys water repellency and reduces tear strength.6 On trail, a breezy, shaded spot is usually better than full sun.
Water repellents and PFAS rules
The EPA lists stain and water repellents on clothing and other fabrics as a source of PFAS,14 long-lasting chemicals that break down very slowly.15 California's AB 1817 names backpacks as textile articles and, from January 1, 2025, bars new ones containing regulated PFAS from being sold there, though outdoor apparel for severe wet conditions is exempt until 2028 if it carries a disclosure.16 Some aftermarket treatments, such as Nikwax's water-based line, are labeled as containing no fluorocarbons.5 Newer finishes may need refreshing on their own schedule, so the drop test is worth repeating.
Frequently asked questions
Are hiking backpacks waterproof?
Almost none are. Most packs use water-resistant fabric but have seams and zippers that leak, and the fabric itself "wets out" in sustained rain. Treat your pack as not waterproof and protect the contents from the inside with a liner or dry bags, rather than trusting the pack alone.
Pack liner or rain cover — which is better?
A liner inside the pack is more reliable, because it protects your gear even when the cover blows off, water runs down your back into the pack, or the fabric soaks through. A rain cover keeps the pack itself cleaner and drier and helps in light rain. Many hikers use a liner as the real defense and a cover as a bonus.
How do I keep my sleeping bag dry?
Treat a dry sleeping bag as non-negotiable, especially a down bag, which loses almost all its warmth when wet. Store it in a dedicated waterproof stuff sack or roll-top dry bag, keep it low and central in the pack inside your liner, and never strap it unprotected to the outside where it catches rain and spray.