Rain Cover vs Dry Bags: How to Really Waterproof Your Hiking Pack

You may have experienced this: you take your pack out after a heavy rain, peel back the rain cover, and discover a soaked jacket and a wet phone inside. How is that possible?

The answer is simple — and it changes everything about how you protect your backpack.

Where Water Really Enters a Backpack

Most hikers assume water gets in from the top. That's partly true, but the main entry points are not where you'd expect.

The three main water entry points:

• The back panel — as you walk in the rain, you lean slightly forward. Water runs down your back, between the pack and your jacket, and soaks directly into the unprotected fabric behind the rain cover.
• Seams — even "water-resistant" technical fabrics have seams. On entry-level packs, these seams are not taped or welded. Water forces through them under pressure.
• Side pockets and zipped openings — standard zippers are not waterproof. After 30 minutes of sustained rain, the side pockets are already damp.

The rain cover wraps the top and sides of the pack. It does not cover the back panel.

The Rain Cover: Essential, But Not Enough

Don't throw out your rain cover. It still serves a purpose: it protects external pockets, reduces water absorption by the fabric, and limits entry from the top. Quality rain covers from Deuter or Osprey even extend over the carry handle.

But its limitations are structural:

• It never covers the back panel
• It doesn't protect against interior seam leakage
• It can tear or blow off in strong winds
• It adds 200–400 g to your load

For a brief 10-minute shower, a rain cover is perfectly adequate. For a multi-hour hike in sustained rain — or any mountain outing in spring and autumn — it doesn't provide sufficient protection.

Internal Dry Bags: The Real Protection

The reliable method is to protect the contents of the pack, not the pack itself. That's where internal dry bags come in.

The concept is straightforward: you store your gear in waterproof bags inside your backpack. No matter how much water enters the pack itself, the contents stay dry.

Roll-top closure bags

These are the gold standard. Bags from Sea to Summit and Ortlieb use a roll-top closure that creates near-perfect waterproofing. They come in multiple sizes:

• XS (1L): phone, power bank, documents
• S (4L): light spare clothing
• M (8L): mid-layer, food
• L (13L): sleeping bag, sleeping mat

These bags can withstand a short submersion. They easily handle several hours of heavy rain.

Compression zip bags

Less waterproof than roll-top models, but useful for dry clothing. They let you compress your insulation layer and pack it neatly.

What volume do you need to protect?

You don't need a separate dry bag for every item. Efficient organisation looks like this:

1. One large bag (8–13L) for clothing
2. One small bag (1–4L) for electronics and documents
3. Everything else (water, food, first aid) tolerates moisture better

The Garbage Bag: The Unbeatable Value Solution

Here's a truth that few gear articles dare to write: a thick 100L bin liner costs €0.30, weighs 40 g, and offers protection equivalent to a €30 dry bag.

The technique:

1. Open your backpack fully
2. Insert a large bin liner inside as a liner
3. Pack all your gear inside it
4. Roll the top of the bin liner closed before closing the pack

This is the method used by many experienced long-distance trekkers, including on the GR20 and multi-day mountain crossings. Its only drawback: it's not suited to frequent pack access.

For bivouacking and multi-day hikes, the bin liner remains the most effective solution. For a day hike with regular pack access, modular dry bags are more practical.

What to Prioritise for Protection

When you're short on space or budget, prioritise:

Critical — protect without exception:

• Phone and power bank
• Documents (ID, insurance, transport card)
• Medications, first aid
• Spare clothing (a soaked jacket at altitude at night can be dangerous)

Important but resilient:

• Food in sealed bags
• Navigation tools (laminated map, altimeter)

Can get wet:

• Wash bag (avoid bar soap that dissolves)
• Clothes you'll change into on arrival
• Spare shoes

The Correct Roll-Top Closure Technique

The most common mistake with roll-top dry bags: not rolling enough. Many people do two folds and consider the bag sealed. It isn't.

The correct technique:

1. Squeeze air out of the bag before closing
2. Fold the collar at least 4 full times (not 2, not 3 — 4)
3. Clip the side buckles firmly
4. If the bag has an air valve, open it to vent residual air before rolling

A properly closed bag with 4 rolls can withstand a 30-second submersion. A bag closed with 2 rolls is merely splash-resistant.

The Optimal Combination for Hiking in Rain

Practical summary by use case:

For more on caring for your pack after a wet outing, see our guide on backpack maintenance. And for everything about hiking in the rain, our guide hiking in the rain covers the full range of solutions.

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Protecting your pack from rain isn't about money — it's about method. A rain cover and a bin liner together cost under €3 and offer superior protection to 99% of €50 solutions sold in outdoor retail chains. Save your budget for what truly matters: good boots and a waterproof jacket.

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