Safety Series - Rule of 120

The Rule of 120: Are You Really Dressed for Cold-Water Paddling? 

Let’s talk about something that could literally save your life on the water—the “Rule of 120” (some call it the Rule of 100 but the principle is the same). Whether you’re a kayaker, a stand-up paddleboarder, or someone who just enjoys floating around with a paddle in hand, this rule helps you figure out when you need to gear up for the cold.  

What Is the Rule of 120?  

The Rule of 120 is a simple equation:  

Air temperature (°F) + Water temperature (°F) = 120º or higher   

Simply put, the Rule of 120 suggests that if the combined air and water temperatures (in Fahrenheit) total less than 120°F, paddlers should take extra precautions, including wearing appropriate cold-water gear. For example:

• Scenario A: Air temp is 60°F, water temp is 45°F. Combined, that's 105°F—time to suit up!

• Scenario B: Air temp is 70°F, water temp is 60°F. Combined, that's 130°F—still chilly, but generally safer

It’s not just about comfort—it’s about survival. Water drains heat from your body 25 times faster than air, so if you fall in, you’ll get cold really fast. And if you're not prepared, things can go south in minutes.  As a point of comparison, the average water temperature on the Potomac River and the Chesapeake Bay is about 45º in the winter months.  Both of these bodies of water can climb to the upper 70ºs in the middle of summer.  

Cold Water Shock: The Danger You Didn’t See Coming   

Hypothermia gets a lot of attention, but cold water shock is the biggest killer in cold-water paddling.  

Here’s what happens when you unexpectedly fall into cold water:  

• Gasp Reflex – Your body panics, and you take a huge, uncontrolled gasp (which is bad if your head goes under).  

• Rapid Breathing – Your breathing rate spikes, and if you’re not careful, you might hyperventilate.  

• Loss of Motor Control – In just one to two minutes, your muscles start to stiffen, making swimming or even grabbing your board difficult.  

• Panic or Cardiac Arrest – In extreme cases, your heart struggles to keep up, which can lead to cardiac arrest.  

A Real-World Case 

In April 2021, a kayaker on Lake Crescent in Olympic National Park tragically lost his life after capsizing in near 50°F water. The sudden immersion likely triggered cold water shock, causing an involuntary gasp reflex and rapid breathing, which can quickly lead to drowning. Even strong swimmers struggle in these conditions as muscle control fades within minutes. Despite rescue efforts, he did not survive—highlighting the critical need for cold-water gear, self-rescue skills, and proper planning. This real-life tragedy is a sobering reminder that cold water doesn’t give second chances—dress for the swim, not just the paddle.  

Source 

The lesson? Cold water doesn’t care how experienced you are. It only cares whether you’re prepared. 

What Should You Wear? (Hint: Not Board Shorts)  

So, what do you need if the air + water temp is under 120°F and you want to extend your paddling season?   

1. Wetsuit or Drysuit   

• Wetsuit: Traps a thin layer of water that your body warms up. Good for cool water.  

• Drysuit: Fully waterproof and keeps you completely dry. Best for cold water.  

2. Base Layers & Insulation  

• Avoid cotton (it stays wet and makes you colder).  

• Go minimal for under a wetsuit. 

• Use moisture-wicking layers under a drysuit.  

3. Neoprene Gloves & Booties   

• Cold fingers and toes = miserable paddling experience.  There are a ton of booties and gloves on the market, make the best decision with this blog post as your guide.  

4. Hat or Hood   

• Your head loses a lot of heat. A neoprene cap or hood helps keep you warm.  

5. PFD (Life Jacket)   

• A non-negotiable. If cold water shock sets in, a PFD keeps you afloat while you regain control.  Click here to see more and choose the right PFD.   

Pro-Tip - Test out your cold water paddling kit in a controlled area before you end up really needing it if/when you fall in.  Find a body of water with cold water and you should be close to shore and get in the water (ideally with a friend nearby).  This will give you an idea of what it feels like in that gear set up immersed in cold water.  

How to Check Water Temperature Before You Go   

You wouldn’t go hiking without checking the weather, right? The same goes for paddling. Here are some apps and websites that help you check real-time water temperatures:  

1. NOAA Buoy Data Explorer (App & Website)   

• Shows live water temperatures from buoys across the U.S.  

• Best for: Coastal paddlers, Great Lakes, and major rivers.  

2. RiverApp (App)   

• Displays river water temperatures and flow rates.  

• Best for: River paddlers and inland SUPers.  

3. Windy (App & Website)  

• Interactive maps with air and water temperatures.  

• Best for: Paddlers who also care about wind conditions.   

Check the water temp before you go, and plan your gear accordingly.  

Final Tips to Keep You Safe  

• Paddle with a buddy – If something goes wrong, you want help nearby.  

• Dress for the water, not the air – Just because it’s sunny doesn’t mean the water isn’t freezing (hence the Rule of 120).  

• Have a way to call for help – A waterproof phone case or VHF radio can be a lifesaver.  

Gear Up with These Cold-Water Essentials   

Ready to upgrade your paddling kit? Here are some must-haves (and yes, these are affiliate links that help support this blog!):  

🔥 NRS Axiom Drysuit – Stay warm, stay dry.  

🔥 3/2mm Wetsuit – Perfect for cool water days.  

🔥 NRS HydroSkin Shirts and Pants –  ideal for mixing and matching   

👉 Shop more of our recommended cold-weather paddling gear here   

Stay warm, stay safe, and happy paddling! 🚣‍♂️🌊  

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