Waterproofing & Rain Protection: Complete Guide

Hiking backpacks are water-resistant, not waterproof: the face fabric sheds light rain thanks to a DWR coating and sometimes a PU or silicone backing, but the stitched seams, zipper coils, and back-panel mesh are not sealed and let water in once rain is sustained or heavy. Only fully taped, roll-top dry bags are genuinely waterproof.

Most hiking packs use ripstop nylon or polyester with a polyurethane (PU) or silicone coating on the inside face and a DWR (durable water repellent) finish on the outside face. That combination beads water off the surface and blocks it from soaking through the weave for a while. It does nothing for the holes a sewing needle leaves at every seam, and it does nothing for a zipper's coil teeth, which pass water even when closed. Packs built from Dyneema Composite Fabric (DCF, formerly Cuben Fiber) are the exception at the fabric level — the laminate itself doesn't wet out — but DCF packs still rely on sewn or taped seams and a roll-top closure instead of a zippered lid to keep water out, so the pack as a whole is only as waterproof as its weakest seam.

A rain cover stretches over the outside of the pack to keep the shell fabric and any gear lashed to the exterior from soaking through; a pack liner lines the inside of the main compartment so the gear inside stays dry no matter what happens to the shell. Most experienced hikers carry both.

A rain cover is an elasticized nylon shell, usually sold separately by size, that pulls over the loaded pack like a shower cap. It blocks direct rain from soaking the face fabric and keeps items strapped to the outside — a sleeping pad, wet-weather layer, or trekking poles in a side pocket — from getting drenched. Its weak point is the back panel: a rain cover can't wrap the side that rides against a hiker's back, so wind-driven rain and water wicking up from a wet trail or a pack set down on damp ground can still reach the pack there. A pack liner, by contrast, is a heavy-duty bag — a trash compactor bag, a contractor bag, or a purpose-built roll-top liner — placed inside the main compartment before packing. It doesn't care what the shell does; if the liner is sealed and the top is rolled or twisted shut, the contents stay dry even if the pack's fabric and seams are soaked through.

• Rain cover: protects the shell and exterior-lashed gear; leaves the back panel exposed; can shift or fill with water in wind
• Pack liner: protects everything inside the main compartment; unaffected by seam or zipper leaks; doesn't protect gear strapped outside
• Combined system: liner guarantees dry gear inside; cover keeps the shell lighter by absorbing less water and shields exterior straps and pockets

Reproof a pack's DWR by washing the pack clean first, since dirt and body oils block a new coating from bonding, then applying a wash-in or spray-on DWR product such as Nikwax Tent & Gear SolarProof (a spray-on treatment made for tents and packs) or a comparable product, and then letting the pack air dry as the label directs. Do not put a pack in a clothes dryer or press it with an iron: Nikwax advises air drying only, and pack makers warn that heat damages coatings, foam and buckles.

DWR wears off gradually through abrasion against brush and rock, sun exposure, and accumulated dirt, so a pack used for weekly trips may need reproofing once or twice a season, while occasional use can stretch that to once a year or less.

Keep electronics dry by packing them inside a dedicated waterproof pouch or a zip-top freezer bag and placing that bag inside the pack liner with the rest of the gear, not in an exterior pocket, since exterior pockets and even "water-resistant" zippered compartments are the least protected part of any hiking backpack.

Phones, cameras, GPS units, and battery packs are the gear most worth double-protecting, since water damage to electronics is usually permanent and often trip-ending. A phone-specific waterproof pouch with a roll-top or clip seal works well for a device used often during the day, since it can stay accessible in a hip-belt pocket while still keeping rain and splashes out. For gear used less often, a simple zip-top freezer bag inside the main pack liner is enough, and the redundancy matters: if the pack liner's seal fails at one corner, the inner bag is still a second barrier. Avoid relying on an exterior pocket alone, even a zippered one, since that's the part of the pack most exposed to rain and least likely to be sealed.