Getting it here is the easy part. Most airlines allow a garment bag as a carry on item if you ask in advance, and cabin crew will often hang it if the flight is not full. Confirm with your airline rather than hoping, and budget for extra baggage if the dress travels in its own case.
What happens after Keflavík is where people get caught. The drive to Reykjavík is around 50 minutes, longer to the South Coast or Snæfellsnes, and a dress folded in a car boot for three hours arrives creased. Ask your accommodation before arrival whether they can steam it or whether there is somewhere nearby that can. Small guesthouses often cannot.
Outdoors, the ground decides the dress. A long train on wet grass wicks water within minutes, on black sand it picks up grit that does not brush out, and on lava it snags and tears. Wind on the South Coast and Reykjanes routinely sits at 15 to 20 m/s, so anything loose will move for the entire ceremony. Fitted silhouettes, detachable trains, and a shorter option for the outdoor portion all solve this. Layer thermals underneath, nobody sees them. Hidden waterproof boots for the walk in, photo shoes once you arrive.
And the question people forget entirely: where do you change if the ceremony spot is remote? There is often no building, no toilet, and no shelter. The realistic answers are getting dressed at the accommodation and travelling in it, changing in a rented camper or large vehicle, or picking a spot with a café or guesthouse within a few minutes' drive. Decide this early, because it quietly rules some locations out.
For hair, styles that sit close to the head hold up. Loose curls and long veils do not. Our packing guide covers layers and footwear for everyone else in the party.