Backpack Rain Covers: The “Love-Hate” Guide to Keeping Your Gear Dry

The rain started an hour ago, and the cover on your pack has already blown loose twice. Now the bottom of the pack feels heavy, and you have a bad feeling about the spare socks inside.

That’s a common way to learn about rain covers, and it usually isn’t your fault. Plenty of hikers pull a cover over the pack once, see that it fits, and never hear about the few details that keep it on and let it drain.

So here’s what you came for: how backpack rain covers actually work, what size to buy, how to keep one on in wind, and when a pack liner is the better tool.

By the end, you’ll know which setup keeps your sleeping bag and dry layers dry, and you’ll be able to check your own cover at home in about five minutes.

Rain Cover, Pack Liner or Dry Bag?

Each one protects against a different kind of wet, so the right choice depends on how hard and how long it rains.

Why Your Pack Isn’t Waterproof on Its Own

A lot of hikers skip the cover because the pack is sold as water-resistant. That word matters. Water-resistant fabric sheds a light drizzle, but it isn’t built to keep out hours of steady rain.

Osprey says as much on its own raincover page: the water-repellent finish on a pack gets you pretty far, and the cover is for downpours and wetter conditions. A pack on its own is built to shed a shower, not to keep your gear dry through a long, wet day.

The Problem with DWR, Zippers and Seams

DWR stands for durable water repellent, a finish that makes water bead up and roll off the fabric. It wears down with dirt, sweat and use, and once it fails, the outer fabric soaks up water instead of shedding it.

Newer finishes are made without PFAS, the fluorinated chemicals older DWR relied on. Gore-Tex notes that its PFAS-free DWR holds up less well against oils, so it needs cleaning and re-treating more often.

Zippers are the usual weak spot. Unless a zipper is sealed, water runs along the teeth into the main compartment, and Sea to Summit’s pack cover FAQ names seams and zippers as the way water gets in.

Step 1: Get the Size Right So the Cover Stays Put

When a cover blows off or sags, check the size first. A cover that’s too big leaves slack fabric that catches wind like a sail, and the loose bottom holds water instead of shedding it.

A cover that’s too small has the opposite problem. It won’t wrap under the bottom of a full pack, so the drawcord sits on the side and works loose as you walk.

Brands size covers by the pack’s volume in liters. Osprey’s Ultralight Raincover, for example, comes in Medium for 30 to 50 liter packs, Large for 50 to 75 and Extra Large for 75 to 110.

For daypacks, Osprey’s Hi-Vis Raincover comes in Extra Small for 10 to 20 liters and Small for 20 to 35.

When to Size Up

Take the next size up in two cases: your pack sits at the top of a size range, or you strap a sleeping pad, tent or other bulky gear to the outside. Either way, the cover has to stretch over the loaded shape, not the liters on the tag.

Past that, bigger isn’t safer. One size up covers the extra bulk, and anything larger brings back the slack that flaps and pools. The cover should hug the loaded pack without pulling, with the drawcord snug all the way around.

If your pack is mostly for the commute or errands in town, you may not need a cover at all. A trash bag inside the pack keeps a laptop and a jacket dry on a short walk in the rain.

Look for a Retention Strap

A retention strap is what actually holds a cover on in wind. It’s a buckle or strap that clips across the shoulder harness or to the hip belt, so the cover is tied to the pack instead of resting on it. Elastic alone is what lets go in a gust.

Not every cover has one, so check the feature list. Sea to Summit puts a keeper strap across the harness on most sizes of its Ultra-Sil cover, while Osprey’s current Ultralight Raincover lists a draw cord for the fit.

Before your first wet hike, put the cover on the fully loaded pack at home, cinch it and clip the strap. If it pulls tight across the corners or leaves a flap you can grab, it’s the wrong size, and that’s far easier to sort out at home.

Step 2: Give Trapped Water a Way Out

Rain doesn’t only land on top of the cover. It runs off your hood and down your back, slips into the gap between your back and the pack, and Sea to Summit notes that wind-driven rain gets in through that same gap.

That water ends up at the lowest point, the bottom of the cover. With no way out, it sits against the base of the pack and soaks through, or wicks into the hip belt padding.

The fix is a drain hole at the bottom of the cover, often a small eyelet called a grommet. Sea to Summit lists one on the base of its Ultra-Sil cover. Some covers have one and many don’t, so it’s worth checking before you buy.

Step 3: Bright Color or Earth Tone?

Cover color looks like a style choice until you think about who needs to see you. Bright orange, yellow or green stands out against forest, rock and fog, so other people on the trail notice you sooner.

During hunting season, that matters more. The National Park Service tells hikers at the St. Croix National Scenic Riverway, where hunting is permitted, to wear blaze orange during hunting seasons. A bright cover adds color on your back, but it doesn’t replace an orange hat or vest.

Earth tones (green, brown, black) suit wildlife photographers and anyone who’d rather blend in at camp. They’re a fine choice, as long as you know you’re giving up being easy to spot.

For most day hikes and first overnights, I’d pick a bright cover, because being easy to see is the more useful trait when the weather closes in.

Step 4: Dry It, Clean It, Check It

Rain covers look tough, but they wear out like any other gear. Mildew, sun and a tired elastic hem are what to watch for.

All three get worse when a wet cover goes back into its pocket and stays there until the next trip.

The Post-Hike Routine

After a wet hike, this takes a couple of minutes:

1. Pull the cover out of its pocket or stuff sack.
2. Rinse it in clean water. If it’s grimy, use a technical gear wash rather than laundry detergent, because Gear Aid explains that the fragrances and softeners in ordinary detergent leave residue that keeps DWR from working.
3. Hang it to dry completely, out of direct sun, before you pack it away.

When water stops beading on the cover, re-treat it with a PFAS-free spray made for synthetic gear.

Osprey recommends Nikwax Tent & Gear SolarProof for its packs, and the pack itself needs the same kind of care, which my guide to washing a backpack walks through.

Check Your Elastic

If the elastic at the hem has gone slack, the cover won’t grip the pack in wind anymore, and you’re back to chasing it down the trail. At that point it’s time for a new one.

And if a cover does blow away, go back for it if you safely can. A cover tumbling down a slope is litter, and Leave No Trace asks hikers to pack out all trash and litter.

Step 5: When a Pack Liner Does the Job Better

A cover handles rain from above and keeps mud off the pack. On a long or windy wet day, though, rain keeps getting in through that gap at your back, so the cover slows water down rather than stopping all of it.

That’s why a common setup keeps the important gear dry from the inside: a liner in the main compartment, and small dry bags for the sleeping bag and sleep clothes.

A down bag that gets wet clumps and loses its loft, the puffiness that traps warm air, so it’s the item most worth protecting.

The cheapest liner is a heavy-duty contractor bag, the thick trash bag sold for construction cleanup. Your sleeping bag and dry clothes go in first, with the top twisted shut, and the rest loads around it as my guide to packing a hiking backpack sets out.

A contractor bag isn’t a dry bag, though: if the pack goes fully underwater at a river crossing, water can still get in. If rain is the norm where you hike, a waterproof daypack is the other route, at the cost of some weight and easy access.

If you’re new to wet-weather hiking, it’s easy to pack your fears and wrap every item in plastic until the pack crinkles with each step. A liner plus two dry bags, one for sleep gear and one for spare clothes, protects what matters.

Before Your Next Rain Hike: A Quick Check

Get your cover out and put it on your loaded pack at home. Then check five things:

• It fits snugly, with no slack flapping at the sides or pooling at the corners.
• It has a drain hole at the bottom, or you know to leave the cord loose.
• The retention strap clips on and holds.
• The elastic at the hem still grips.
• It’s clean, dry and doesn’t smell of mildew.

If any answer is no, sort it out now, while you’re dry and have time to adjust the cord or swap the cover.

If the check shows it’s time for a new cover, my roundup of the best backpack rain covers is the place to compare them side by side.

And if you’re still building your kit, my list of hiking essentials for beginners shows what else is worth carrying.