The short version
- If thunderstorms are forecast, don't go out. If you can hear thunder, you're within striking distance. Head for shore right away.
- Lightning can strike 10–15 miles from the storm, often under blue sky. Wait 30 minutes after the last thunder before going back out.
- Most lightning deaths and injuries on boats happen on small boats with no cabin, which describes every paddleboard and kayak.
- Learn the four marine products that matter: Small Craft Advisory, Special Marine Warning, Gale Warning and Storm Warning.
- Wind is the hazard that catches paddlers most often. Watch for offshore wind, wind against current, and the trip home into the wind.
Weather on the water does two things that weather on land doesn't. It moves faster across open water with nothing to slow it down, and it leaves you nowhere to shelter. A summer afternoon on a lake can go from glassy to whitecaps and lightning in less time than it takes to paddle back to the launch. The good news: most weather that hurts people on the water was forecast, visible, or both. This guide covers how to read the forecast, what the sky is telling you, and exactly what to do when a storm finds you anyway.
Before you launch: reading the marine forecast
For coastal waters and the Great Lakes, use the National Weather Service marine forecast for your zone, not the city forecast. It gives wind in knots, wave heights and any active advisories. For inland lakes and rivers, use your local NWS office forecast and the hourly graph, and watch the wind and thunderstorm lines closely.
The marine alerts that matter
| Product | What it means (NWS definition) | What paddlers and small boats should do |
|---|---|---|
| Small Craft Advisory | Sustained winds or frequent gusts in a range set by region (for example, 20–33 knots in the southern US, 22–33 knots on the Great Lakes, 25–33 knots in much of the East), and/or hazardous seas | Paddlecraft and small boats stay in. Conditions well below this level are already serious on a SUP or kayak. |
| Special Marine Warning | Short-lived hazard (up to 2 hours): thunderstorm winds or gusts of 34 knots or more, hail of 3/4 inch or larger, or waterspouts | Get off the water or to the nearest safe harbor now |
| Gale Warning | Sustained winds or frequent gusts of 34–47 knots (39–54 mph) | Recreational boats stay in port |
| Storm Warning | Sustained winds or frequent gusts of 48–63 knots (55–73 mph) | Everyone stays in |
One knot is about 1.15 mph. A forecast of "15 knots gusting 25" means gusts near 29 mph. That's a hard day in a kayak and a very hard day on a paddleboard.
Look at the hourly forecast, not just the daily summary. Summer thunderstorms on lakes often build in the early to mid afternoon. An early start that has you off the water by lunchtime avoids most of them, and the wind is usually lighter in the morning too.
Wind: the hazard that catches paddlers most
Lightning gets the headlines, but wind is what usually turns a nice paddle into a rescue. Watch for these patterns:
- Offshore wind. Wind blowing from land out over the water feels calm at the beach because the land shelters you. Fifty yards out, it's stronger, and it's pushing you away from shore. Beginners and inflatables are especially vulnerable.
- The trip home. If the wind is behind you on the way out, you'll be paddling into it, tired, on the way back. Start your trip heading upwind.
- Wind against current or tide. When wind blows against moving water, waves get steep and short, even when the wind speed looks modest.
- Gusts. A forecast average hides gusts. Plan for the gust number, not the average.
- Fetch. The longer the stretch of open water the wind blows across, the bigger the waves. The far side of a big lake can be very different from your sheltered cove.
Our desk's rule of thumb: beginners on SUPs and recreational kayaks are happiest in winds under about 10 mph, with no offshore component. Experienced paddlers with touring gear can handle more, but they make that call with a plan, not a hope.
Reading the sky once you're out
Forecasts miss things. Keep watching, especially upwind, which is usually the direction you aren't facing.
- Towering cumulus that grows taller through late morning and early afternoon, with hard, cauliflower-like tops, is a storm building.
- An anvil top spreading out from a tall cloud means a mature thunderstorm. Lightning can travel well outward along the anvil.
- A dark, low shelf or roll cloud on the leading edge means a gust front. The wind will arrive before the rain, and it can be violent.
- A sudden temperature drop or wind shift, or a dark line moving across the water toward you (a "cat's paw" of gusts), means wind is minutes away.
- Static on an AM radio or flickers in the distance mean lightning is active, even if you can't hear thunder yet.
Lightning: the numbers that matter
| Fact | What it means for you |
|---|---|
| Thunder can usually be heard only about 10 miles from the strike | If you can hear thunder, you're close enough to be struck |
| "Bolts from the blue" can strike 10–15 miles from the storm | Blue sky overhead doesn't mean you're safe |
| Flash-to-bang: seconds ÷ 5 = miles | 15 seconds is about 3 miles. Use it to judge distance, but NWS says not to stand outside counting. Start moving. |
| About half of successive flashes land roughly 9 km (5.6 miles) apart. NWS recommends staying 6–8 miles from the previous flash. | The next strike can land well beyond the last one |
| 30-minute rule | Wait 30 minutes after the last thunder before going back out |
The National Weather Service is blunt: water and metal don't attract lightning, but they're excellent conductors of electricity. And there is no safe place outside when thunderstorms are in the area.
NWS reports that the vast majority of lightning injuries and deaths on boats happen on small boats with no cabin. That includes every paddleboard, kayak, canoe, jon boat and open bowrider. Your only real protection is getting off the water and into a safe building or hard-topped vehicle before the storm arrives.
What to do when a storm catches you
On a paddleboard, kayak or canoe
- Head for the nearest shore immediately, not necessarily your launch. Any safe landing will do.
- On a SUP, kneel or sit to lower your profile and stay stable in gusts. Keep your life jacket on and your leash attached.
- Once ashore, get away from the water, wet gear and metal. Get into a building or hard-topped car if one is reachable. If not, avoid open beaches, isolated tall trees and high points, and spread your group out so one strike can't hit everyone.
- Stay off the water until 30 minutes after the last thunder.
On an open powerboat
- Head for the nearest safe harbor or shore at a safe speed. Everyone wears life jackets.
- If you can't reach land, NWS advises dropping anchor and getting as low as possible in the boat.
- Stay away from metal fittings, keep hands out of the water, and use the radio only for emergencies.
On a cabin boat
NWS says large boats with cabins are relatively safe, especially those with properly installed lightning protection systems. Stay inside the cabin, away from metal surfaces, and off the radio except in an emergency.
Snorkeling and diving
Swimmers should get out of the water and away from it. For scuba divers on a boat without a usable cabin, NWS notes they're safer diving deep for the duration of the storm, or as long as possible.
Other weather hazards worth knowing
- Fog: You lose sight of shore and other boats. Carry a compass or GPS, a sound signal and a light. Stay close to shore, or don't go.
- Waterspouts: They often form along cloud lines over warm water. If you see one, move away at right angles to its path. NWS issues Special Marine Warnings for them.
- Heat: Reflection off the water raises sun exposure and dehydration. Plan for shade, water and UPF clothing.
- Cold water under warm air: Spring and fall are prime time for cold-shock accidents. Read Cold Water Shock and the 1-10-1 Rule.
- Surf zone: Building swell, rip currents and shorebreak are their own forecast skill. See How to Read a Surf Forecast.
Weather gear for small craft: a phone in a waterproof case with a radar app and NWS alerts turned on, a waterproof handheld VHF with weather channels on bigger water, a whistle, and a light shell jacket in a dry bag. Rain plus wind cools you fast, even in summer.
Shop the gear: Waterproof tech & radios · Life jackets & safety
A simple go/no-go table
| Condition | Call |
|---|---|
| Thunderstorms in the forecast for your time window | No go |
| Any advisory or warning for your zone | No go for paddlecraft and small boats |
| Offshore wind, plus beginners or inflatables | No go, or stay inside a sheltered cove |
| Gusts well above your group's comfort level | Reschedule or switch to a sheltered spot |
| Thunder heard | Off the water now. Wait 30 minutes after the last rumble. |
| Light wind, clear forecast, water temperature checked | Go, and keep watching upwind |
Pair this with the full pre-outing safety checklist.
FAQ
Is it safe to swim when there's thunder in the distance?
No. If you can hear thunder, you're within striking distance. The National Weather Service advises getting out of the water and away from it, and waiting 30 minutes after the last rumble before going back.
Does a carbon paddle or metal boat attract lightning?
Lightning isn't attracted to water or metal, but both conduct electricity very well. What matters is being the tallest thing on open water, and being out there at all. Get off the water instead of worrying about your paddle.
What wind speed is too much for paddleboarding?
There's no official cutoff. Our rule of thumb for beginners is under about 10 mph with no offshore component. Experienced paddlers handle more, but conditions well below a Small Craft Advisory can already be dangerous on a board.
How long should I wait after a storm before going back out?
At least 30 minutes after the last thunder you heard. If thunder keeps rumbling, the clock resets every time.