When the Heat Index Hits 110°F: Why Autoimmune Disease and Heat Don't Mix

Summer in Florida is hot every year, but when the heat index climbs to 110°F or higher, it becomes more than uncomfortable, it can become dangerous.

If you live with rheumatoid arthritis, lupus, psoriatic arthritis, Sjögren's syndrome, vasculitis, or another autoimmune condition, you may notice that extreme heat affects you differently than it does your family or friends.

That's not "just getting older" or "being out of shape." There are real reasons your body may struggle more in extreme heat.

What Does a 110°F Heat Index Actually Mean?

The heat index combines the actual air temperature with humidity to estimate how hot it feels to the human body.

High humidity prevents sweat from evaporating efficiently. Since evaporation is your body's primary cooling mechanism, your internal temperature rises much faster.

In Florida, it's common for the actual temperature to be in the mid-90s while the heat index exceeds 110°F.

Why Autoimmune Conditions Can Make Heat Harder to Tolerate: Autoimmune Disease and Heat

Autoimmune diseases often affect much more than the joints.

Many people also experience:

• Chronic fatigue

• Dysautonomia

• Inflammation

• Medication side effects

• Difficulty regulating body temperature

Some medications commonly used to treat autoimmune diseases—including steroids, biologics, methotrexate, and certain blood pressure medications—may increase dehydration risk or reduce your body's ability to respond to heat.

For some patients, even a short period outdoors can trigger hours, or even days, of increased fatigue or worsening symptoms.

Signs Your Body May Be Overheating

Pay attention if you notice:

• Sudden exhaustion

• Increased joint pain

• Dizziness

• Headache

• Rapid heartbeat

• Nausea

• Brain fog

• Muscle cramps

• Excessive sweating or suddenly stopping sweating

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If symptoms become severe, such as confusion, fainting, chest pain, or difficulty breathing, seek emergency medical care immediately.

Six Ways to Prepare for Extreme Heat

1. Start Hydrating Before You Go Outside

Don't wait until you're thirsty.

Begin drinking fluids well before heading outdoors, and continue replacing fluids throughout the day.

If your physician has recommended electrolyte replacement, follow those recommendations as well.

2. Plan Your Day Around the Weather

Whenever possible:

• Schedule walks early in the morning.

• Run errands before noon.

• Avoid prolonged outdoor activities between late morning and early evening.

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Sometimes shifting your schedule by just a few hours can dramatically reduce heat exposure.

3. Dress for Cooling

Choose:

• Light-colored clothing

• Loose-fitting fabrics

• Wide-brimmed hats

• Cooling towels around your neck

• UV-protective clothing when appropriate

4. Build Cooling Breaks Into Your Routine

Don't wait until you feel overheated. If you're shopping, attending an event, or working outdoors, plan regular breaks inside air conditioning. Even ten minutes indoors can help lower your body temperature before symptoms worsen.

5. Keep a "Heat Safety Kit"

Consider keeping these items in your vehicle or bag:

• Water bottle

• Electrolyte packets

• Cooling towel

• Small portable fan

• Sunhat

• Sunscreen

• Extra medications if appropriate

Planning ahead can make a big difference.

6. Listen to Your Body

One of the biggest mistakes people make is trying to "push through."

If fatigue suddenly worsens or your joints become more painful, those may be early warning signs that your body is struggling. Resting early often prevents much bigger problems later.

Give Yourself Permission to Slow Down

Many people with autoimmune diseases feel guilty for canceling plans or staying indoors during extreme heat, but protecting your health isn't being lazy. It's recognizing that your body is working harder than most people realize.

When Florida's heat index reaches 110°F, everyone should take precautions. If you live with an autoimmune condition, those precautions become even more important.

Staying cool, staying hydrated, and listening to your body's signals can help you avoid heat-related illness and reduce the likelihood of a symptom flare.

The Living Radiantly Patient Perspectives series exists to give voice to the real experiences of people living with rheumatic, autoimmune, and chronic illnesses. This week's article comes from our practice. We have had many conversations with patients regarding the extreme heat and thought it would be beneficial to share the information here. If you have a story, insight, challenge, or triumph you'd like to share, we welcome your contribution. Together, we can help others feel seen, understood, and less alone throughout Clermont, Florida, and the surrounding communities.