In August 2011, I went on a kayak trip with Tampa Bay Sea Kayakers. We launched in the morning at Sunset Beach in Tarpon Springs. It was one of our usual trips to Anclote Key, a 3-nautical-mile open-water crossing. We planned to paddle around the southern point and up the west coast for a stop on the beach. After swimming, rescue practice and a snack break, we would return for a round trip of approximately 8 nautical miles.
This was a typically hot summer day in Florida with sunny skies, temperatures in the mid-90s, a light
westerly breeze of less than 5 knots and water temperature in the high 80s. The trip over into the wind was pleasant, and we reached our destination in about an hour and a half.
After loafing on the beach and in the water, we loaded up and started our return trip just after noon. We paddled south down the Anclote coast with a light wind on our beam, but as we turned around the point to the east, the conditions changed drastically. We were now paddling with the wind, so the apparent wind for us was virtually zero. A line of thunderstorms was also building along the mainland coast, our destination, about 3 nautical miles ahead.
Now we all felt intense oppressive humidity, and after about a mile of paddling, several paddlers, including me, started feeling the effects of heat stress. The snacks we had eaten on the island provided sufficient electrolytes while maintaining plenty of hydration throughout; however, the heat and humidity were preventing the normal evaporation of sweat. Later study of the weather factors and heat index tables indicated the “feels like” temperature may have been near 113 degrees Fahrenheit! I realized that I was generating more heat than my body could dissipate. I had plenty of water and was sweating profusely, yet I still felt that I was overheating.
I felt slightly headachy, and fellow paddlers told me that my forehead and face were red. I asked another paddler to let me do a “bow dip,” in which I held onto the bow of his boat and rolled over into the water. As I lay in the warm water, I remember thinking that this was like trying to cool off in a hot tub. Subsequent bow dips in the warm water provided little relief for anyone in our group. This became a serious concern as we had about 2 more miles to cover, which at normal cruising speed would be over 40 minutes of continued paddling in these conditions.
Our group decreased paddle speed to a slow pace, continued drinking plenty of water and occasionally stopped for a bow dip. When we finally got to the beach, about half the group were experiencing symptoms of heat stress, a couple of paddlers had run out of water and one person appeared in serious shape. We got them under a beach shower immediately, and soon we all took turns trying to cool off under the shower. Fortunately, we were able to cool down in time, and no one experienced any long-term effects from this incident, but we all learned some serious lessons about paddling in heat.
Each summer we see incidents in which young athletes succumb to heat illness while practicing football or other strenuous school sports. As a result, there’s a lot of research regarding the signs and symptoms of heat stress, how to avoid it and how to treat it. Unfortunately, there is little comparable research focused on heat stress while on the water. In most cases, one can simply get into the water to cool off, but what happens when a paddler starts to overheat, the water is very warm and they are in a remote location?
Research reveals that the human body vents heat through three mechanisms: breathing, sweating and blood flow to the body surface. Maintaining proper hydration is important to allow for sweating. Sweating cools the body through evaporation, which carries off the heat transported by blood flow. However, as humidity increases and wind decreases, evaporation is progressively hindered, reducing the body’s ability to vent heat and cool itself. During high heat and humidity, despite adequate hydration and electrolytes, the body heat generated through exertion (paddling) can quickly overwhelm the body’s cooling capacity. Similar to an automobile engine, if the body is producing more heat than the cooling system can effectively dissipate, then the body is on its way to breakdown in the form of heat illness. This may involve a number of heat stress disorders such as heat exhaustion and heat stroke.
Some initial symptoms of the onset of heat illness are heavy sweating, headache, nausea, dizziness, weakness, increased body temperature and pulse rate. Paddlers noticing these symptoms should take immediate action to prevent a possibly life-threatening situation. For more detailed information regarding types of heat disorders, symptoms, first aid, prevention and safety tips, go to NOAA-NWS Heat.
Rescue
Once a paddler starts to experience symptoms of heat stress, the exertion should be terminated immediately, and steps must be taken to cool the body before it escalates into more serious heat illness. This means stopping the paddle and preferably getting the person into cool water. Rescue is easy if paddling on a shady flowing river or inland water where water temperatures remain in the low 80s or below and land is nearby. For example, Florida’s spring-fed Rainbow River averages 72 degrees year-round and is a popular place for water sports during the summer. Suffering the effects of heat stress is not likely in this environment.
In the incident described earlier, we were in open warm water with no shade and far from land. The
average human body temperature is around 98.6 degrees, so as water temperature warms to body temperature, its ability to cool an individual displaying symptoms of heat stress lessens. Trying to tow an individual suffering from heat stress to safety would also subject the rescuers to dangerous overheating. If a situation escalated to a point of serious danger in open water, the only viable option would be to make a distress call on marine VHF radio.
Mitigation
The best way to avoid heat stress while paddling is to avoid the conditions that could cause a problem. Due to the incident described earlier, I no longer run open-water trips during the summer where there is a possibility of encountering weather conditions causing a high heat index that could become dangerous.
From my experience, I now consider four factors to help make the go/no-go decision on a paddle trip during hot weather. If all four factors are present or could occur during a trip, there is potential
for paddlers to encounter heat stress that could become dangerous:
- high air temperature (high 80s and above)
- high humidity (dew point of 65 and above)
- low wind or apparent wind (5 knots or less)
- high water temperature (high 80s or above)
HELPFUL LINKS
Paddlers can obtain current information on each factor at the following links:
Paddlers should take precautions when paddling in hot weather:
- Carry and use adequate hydration and electrolyte drinks.
- Plan trips to start earlier in the morning and end before the
midday heat. - Reduce trip distance and paddle speed.
- Avoid long downwind legs on a trip.
- Avoid the “doldrums” typically found adjacent to building storms
and during the transition period between a morning breeze and
the afternoon sea breeze. - Avoid getting caught in open water or remote locations where
rescue of a paddler experiencing heat illness would be difficult.
Much research has been done on cold-water immersion and the effects of hypothermia, which has caused many boater fatalities over the years. Paddlers who paddle in warm climes also need to beware of the effects of hyperthermia, which poses a serious, even fatal, threat to the health and safety of paddlers. Understanding the issue and taking proper precautions can lead to safe paddling trips in warm weather.
