What Should You Do During Sudden Heavy Rain on a Trek?

Safety and nature · Hiking, trekking and nature · 2 min read · Researched guide · Last updated 2026-10-23

In short: In sudden heavy rain, move away from streams, dry gullies and slot canyons, because flash floods can arrive within six hours of the rain and can start miles from where it rained. Avoid crossing swollen water, keep clear of ridges and lone trees if there is lightning, stay warm and turn back early.

Quick facts

Move away from water

Flooding can occur many miles from the rain that caused it, and in dry washes or creek beds a stream can form within seconds even under clear skies. Climb to higher ground and stay out of gullies, slot canyons and stream beds. Danger is greatest after dark.

Do not cross floodwater

The standard advice is to turn around rather than try to cross. A swollen stream that was ankle-deep in the morning may be impassable by afternoon. See river crossing judgement.

If there is lightning

• Take precautions when the gap between flash and thunder is 25 seconds or less (about 8 km).
• Avoid ridges, open ground, lone trees and metal poles.
• Spread the group out; do not huddle.
• If you cannot reach shelter, crouch with feet together on low ground.
• Tents and sheds are not safe; a hard-topped vehicle is.

Stay warm and decide early

Wet and wind chill can cause hypothermia. Put on a rain layer before you are soaked, eat and drink, and turn back early instead of pressing on. Check forecasts with forecast guidance, and carry the items in the day hike packing list and a first-aid kit. Dial 112 for emergencies.

Check before you go

This is a researched safety guide, not a substitute for training or local advice. Rules, permits, closures and fees change. Confirm locally before you travel.

Frequently asked questions

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Rules, closures, fees and conditions change. Confirm with the relevant authority before you travel, and treat this guide as planning help, not a substitute for local advice.