A heat wave is a period of unusually hot weather that lasts long enough to threaten health, buildings, transportation, and power systems. Heat waves matter because the human body must keep its internal temperature near 37°C to function safely. When air temperature, humidity, and strong sunlight stay high, the body can overheat faster than it can cool down.
Good preparation helps students, families, and communities avoid heat illness and respond quickly in an emergency.
The body cools mainly by sweating and by moving heat from warm skin to cooler air, but humid air slows evaporation and makes sweating less effective. The heat index combines air temperature and relative humidity to estimate how hot conditions feel to the body. During a heat wave, safe actions include drinking water often, limiting outdoor exercise, using shade or air conditioning, checking on vulnerable people, and recognizing warning signs of heat illness.
Emergency preparedness also means knowing cooling center locations, keeping phones charged, and having a plan if power fails.
Key Facts
- Normal core body temperature is about 37°C or 98.6°F.
- Temperature conversion formulas are °F = 1.8°C + 32 and °C = (°F - 32) / 1.8.
- Heat index depends on air temperature and relative humidity, so 35°C can feel much hotter when humidity is high.
- Evaporation removes heat from the body because liquid sweat absorbs energy when it becomes water vapor.
- A simple hydration guideline during heat is to drink water regularly before thirst becomes strong, especially before and after activity.
- Call emergency services if someone has confusion, fainting, seizures, hot skin, or a very high body temperature because these can signal heat stroke.
Vocabulary
- Heat wave
- A heat wave is a period of abnormally hot weather that lasts for days and can create health and safety risks.
- Heat index
- The heat index is a measure of how hot the air feels to the body when temperature and humidity are considered together.
- Humidity
- Humidity is the amount of water vapor in the air, and high humidity makes it harder for sweat to evaporate.
- Heat exhaustion
- Heat exhaustion is a heat illness that can cause heavy sweating, weakness, dizziness, nausea, and headache.
- Heat stroke
- Heat stroke is a life-threatening emergency in which the body overheats and may cause confusion, collapse, or loss of consciousness.
Common Mistakes to Avoid
- Waiting until you feel thirsty to drink water is a mistake because thirst can lag behind fluid loss during hot weather.
- Assuming shade alone makes intense heat safe is a mistake because hot air and high humidity can still cause overheating.
- Exercising at midday during a heat wave is a mistake because solar radiation and air temperature are usually strongest then.
- Ignoring confusion or fainting as simple tiredness is a mistake because these can be warning signs of heat stroke that need emergency help.
Practice Questions
- 1 Convert 40°C to degrees Fahrenheit using °F = 1.8°C + 32.
- 2 A student drinks 250 mL of water every 30 minutes during a 3-hour outdoor event. How many milliliters of water does the student drink in total?
- 3 Explain why a 32°C day with high humidity can be more dangerous than a 35°C day with low humidity, even though the air temperature is lower.