What you wear matters more than where you go.

These are not the same, no matter how loosely product pages use them. Waterproof shells have taped seams and a rated hydrostatic head (10,000mm and up handles sustained rain); water-resistant pieces shed a light shower and then wet out. For genuine downpours you need waterproof with sealed seams. The trade-off is breathability — fully waterproof fabrics trap more sweat, so match the rating to the actual weather you face rather than buying the most bomber option by default.

Your base layer's job is moving sweat off your skin so you stay warm and don't chill on stops. Merino wool resists odor remarkably well and regulates temperature across a wide range, making it ideal for multi-day trips; synthetics dry faster and cost less but hold smell. The one rule with no exceptions: never cotton next to skin in the cold — it soaks up sweat, stops insulating, and pulls heat away from your body.

Down offers the best warmth for its weight and packs down small — measured in fill power, where higher numbers mean more loft per gram. Its weakness is moisture: wet down collapses and stops insulating. Synthetic insulation is heavier and bulkier but keeps working when damp and costs less. Choose down for dry cold and weight-critical trips, synthetic for wet climates or hard-use pieces you can't baby.

A shell needs room for layers underneath without being a tent; a base layer should be close-fitting to wick effectively. Consider the full system when sizing — an athletic-cut jacket that fits over a t-shirt won't close over a fleece and down layer. Check that arms stay covered when you reach overhead and that hems don't ride up, because the coldest, wettest gaps are the ones that open when you actually move.