Once I moved to the Bay Area, however, I began to love being outside. Exploring hiking trails in Northern California was a cool and welcome treat.

But as the years progressed, my sensitivity to heat increased. Anything hotter than 70 degrees was too much for me. At first, I was just uncomfortable and would seek out air-conditioning. But one June day, about 16 years ago, I hit bottom. On a work trip in Monterey, I spent a sleepless night in a quaint hotel with no air conditioning. At my morning meetings, I felt queasy. During the drive home, my car’s air conditioning was inadequate, and as soon as I entered my home, I felt sick. I mean really sick. Did I have food poisoning? Or was this part of my myotonic dystrophy?

Alone and terrified, I called 911. Once in the hospital, I struggled to tell the doctors about my condition because I could barely speak. I remember vomiting a few times and falling into a deep sleep. I now do anything I can to avoid the heat.

Shortly after that experience, I moved to a new house and installed central air-conditioning—an expense I’ve never regretted. Without it, my energy wanes and my strength diminishes, which affects my speech, breathing, and ability to move. It’s scary, and then the anxiety kicks in.

Surprisingly, few of my friends with my condition experience heat sensitivity; they are much less tolerant of cold weather. But I’ve talked to people with multiple sclerosis and spinal cord injuries who can’t tolerate heat and have learned a few tips from them.

Beyond the usual strategies—avoid the sun during peak hours, maintain hydration, and wear light-colored, loose-fitting clothes—I’ve heeded their advice and tips from health care professionals as well.

1. Eat smart. 
   On hot days, especially when I need to be outdoors temporarily, I eat light foods with a high water content such as cucumbers, strawberries, tomatoes, celery, grapefruit, watermelon, summer squash, and lettuce. I avoid dairy, wheat, and other foods that make me feel bulkier.
   
2. Dress wisely.
   I wear special headscarves that have beads that swell when dipped in water. Sometimes I just pour water on top of my head and let it drip. Sure, I look dorky, but it helps. Although I prefer to wear cotton clothes, wickable fabrics, which tend to be synthetic, work better for evaporating perspiration from my skin.
   
3. Breathe deeply.
   Meditating doesn’t cool me down when I’m hot but it can help quell my anxiety. Whenever I start to get uncomfortable, I turn inward and focus on my breathing, making sure my inhalation is deep and my exhalation is longer than the inhale. Or I choose one of the guided audio meditations on my iPhone. Many are available to download free.
4. Spot the shade.
   In addition to checking the local temperature, I scout out where the shade is as I navigate from point A to point B. If a shaded path is longer than one through direct sun, I take the longer path.
5. Plan carefully.
   Peak sun is generally between noon and 4:00 p.m., so I try to schedule activity either around dawn or dusk. It’s generally cooler and quieter. If I’m attending an outdoor event, I get there early to avoid the mass of humanity. Not being jostled by crowds helps me reserve my energy.
   
6. Order in.
   If it’s been a particularly hot day and I haven’t had the energy to shop, I’ll order groceries online. It not only saves time and energy, but everything arrives chilled at my doorstep. If I want a hot meal without disrupting my kitchen climate, I have plenty of delivery options for that too.
   
   

Until I find some magic potion that can alter my heat sensitivity, I’ll wait for that sunny 65-degree day for my next walk in the park.

Leslie Krongold, EdD, lives in Alameda, CA, where she leads support group meetings for the Myotonic Dystrophy Foundation. She also writes a blog and produces a podcast series called Glass Half Full.

An Expert Weighs In

BY BRUCE COHEN, MD, FAAN

As Leslie Krongold notes, heat sensitivity is not a common symptom of myotonic dystrophy. But the symptoms she describes—fatigue, exhaustion, vomiting, weakness, and decreased ability to function—are very common in my patients with neuromuscular diseases and are extremely important to recognize and treat.

Know the Heat Index

We are most comfortable when our body heat is dissipated into the surrounding environment. Leslie says that a sunny day of 65 degrees is best for a walk, but if the humidity were 95 percent and there was no wind, she might have been uncomfortably hot. Conversely, if the humidity were low but there were heavy clouds and a strong breeze, she might have been too cold.

Everyone’s discomfort worsens with higher humidity, but dangerous levels of heat exposure are based on the combination of ambient temperature (the temperature taken in the shade) and humidity, with some influence from wind and sun intensity. I advise my patients to check the heat index, which takes these factors into effect. 

Here are a few more recommendations:

1. Drink cool water.
   Cool water is almost guaranteed to make you feel better and will prevent dehydration.
2. Wear a cooling collar.
    Cooling collars, which are available at camping stores and in the Outdoors sections of department stores, contain dry crystals that are activated with water. When worn around the neck the water quickly evaporates and pulls heat from the neck. Or wear a cooling vest, which have pockets for inserting frozen packs. The proximity of these frozen packs next to the body really helps.
3. Use fans.
   A handheld or portable fan helps your body evaporate sweat.
4. Take a bath.
   

   Soaking in the bathtub, using comfortable temperature water, will cool you down quickly. No cold water needed.

Dr. Cohen is director of the NeuroDevelopmental Science Center at the Children’s Hospital Medical Center of Akron in Ohio and a member of the editorial board of Brain & Life.