(Editor's Note: This article was originally published onJuly 7, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
What is Extreme Heat?

In weather-related situations, heat waves are a leading cause of death. Two or more weeks of temperatures that range 10 degrees or more above the average for a region is considered a "heat wave." The Center for Disease Control Emergency Preparedness & Response registered 8,015 U.S. deaths between 1979 and 2003 that were due to excessive heat exposure. Symptoms and treatment are described later for the four main heat-related conditions: dehydration, heat cramps, heat exhaustion, and heatstroke.

Most of us (except the proverbial mad dogs and Englishmen) don't go out in the midday sun, but gardening tasks must be completed if we don't want to lose control of our gardens. When temperatures soar, be prepared to make some adjustments in your gardening, weeding, and watering schedule.

Prevention is the Best Cure

Get that gardening done while it's cool! During extremely hot weather, limit outside physical activity to before 10 a.m. and/or late afternoon (after 4 p.m.)

Follow the shady spots around your property and let Nature help keep you comfortable.

Drink 'til your teeth float! Whether you're thirsty or not, drink 16 to 32 ounces of water or fruit juice per hour during exercise in hot weather.

Avoid caffeine, alcohol, and high-sugar drinks while working in hot weather; these speed up fluid loss and make you feel no

Work a little slower - it'll still be there later.

If you feel too hot, move into the shade to rest, or go inside to cool down.

Wear lightweight, loose-fitting clothing made of natural fibers such as cotton or linen.

ALWAYS wear a hat with a brim. This will protect not only the top of your head, but shade your face and neck. Body heat escapes through the scalp, so try to find a light-weight or vented sunhat to help keep your head cool.

Sunglasses will protect your eyes from both glare and dust.

Sunscreen of SPF15 or higher should be applied before going outside, especially on a cloudy day when the lack of rays can fool you.

Use insect repellent, especially in the early morning hours when the mosquitoes are active.

Who is At Risk?

Even healthy folks can become victims to dehydration, heat cramps, heat exhaustion, or heatstroke. For older gardeners (65+) and those with chronic illnesses, hot weather is not a friend. Why? As we age, our bodies may not be able to manage heat stress and, in the case of the elderly, the body might not sense the temperature change or respond to it. Some medications also prevent the body from regulating internal temperatures when the weather is hot.

What are the Symptoms of Heat-related Conditions?

We all know what dehydration is, but did you know that by the time you are "thirsty," you are already dehydrated? Severe dehydration can lead to kidney failure, or become life-threatening.
  • Dry mouth
  • Increasing thirst
  • Weakness and/or lightheadedness
  • Decrease in urination
  • Dark urine
Advanced symptoms (especially in children or the elderly)
  • No tears
  • Sunken eyes
  • Skin that does not spring back when pinched
  • Begin rehydrating as quickly as possible; notify your physician for further instructions.

Heat Cramps
During heavy sweating, salt and moisture are depleted, and it is believe that this is the cause of the muscle pains or spasms known as heat cramps. They are usually associated with strenuous exercise and affect the abdomen, arms, or legs. Individuals with heart problems or those on low-sodium diets should seek medical attention immediately for heat cramps.
  • Stop activity
  • Move to cool environment
  • Drink clear fruit juice
  • Wait a few hours after the cramps subside before returning to activity
  • If cramp does not subside within an hour, seek medical attention

Heat Exhaustion
Occurring indoors or outdoors, with or without exercise, heat exhaustion is the result of long periods of exposure to very warm environments. Excessive sweating drains the body of fluids and electrolytes (salt and minerals). Left untreated, heat exhaustion can progress to heatstroke - a life-threatening or disabling condition.
  • Heavy perspiration
  • Cool, clammy skin
  • Dizziness
  • Headache
  • Nausea
  • Abdominal cramps
  • Shallow Breathing
  • Muscle tremors
  • Move immediately to an air-conditioned environment, if possible, or to a shady spot outdoors
  • Drink cool non-alcoholic or decaffeinated beverages.
  • Loosen clothing
  • Stay quiet for at least an hour
  • Individuals with heart problems or high blood pressure should contact their physician

When the body becomes unable to control its internal temperature, the sweating mechanism fails and the body is unable to cool down. Within 10 to 15 minutes, the core temperature can rise to 106 degrees F or higher. The most dangerous of the heat-related conditions, untreated heatstroke can cause death or permanent disability.
  • Rapid pulse
  • Throbbing headache
  • Dizziness
  • Red, hot, dry skin
  • Nausea
  • Confusion
  • Body temperature above 103 degrees F (taken orally)
  • Unconsciousness
  • Move victim to an air-conditioned space, or shady spot outdoors
  • Seek medical attention immediately
  • Do not give the victim fluids to drink
  • Loosen clothing
  • Position person in a semi-sitting position
  • Bathe head and body with cold water, or mist victim with garden hose

One Last Caution
While the thrust of this article is aimed at gardeners, remember that infants and children are also highly susceptible to heat-related conditions. Always consult a physician immediately if you suspect that a child is suffering from the heat.

HealthBeat, Illinois Department of Health, April 2007, 2008
Center for Disease Control Emergency Preparedness & Response Website,
Santa Clara County Hot Weather Tips