Overview

A heat wave is 3 or more days in a row when the maximum temperature is 32°C (89.6°F) or more. Everyone has an increased risk for a heat-related illness during a heat wave. Extensive exposure to extreme heat can result in serious medical conditions such as heat cramps, heat exhaustion and heat stroke.

A heat-related illness can be more serious for:

• Older adults, who may not notice excessive heat, do not sweat as effectively, or do not feel thirsty.
• Small children, who can't transfer heat very well.
• People with chronic medical conditions.
• People taking medicines, such as heart medicines or tranquilizers, for serious psychiatric disorders or depression.
• People with weight problems.
• People with alcohol or drug use problems.
• People with mental health or developmental problems.
• People who work in the heat.
• People who exercise in the heat.
• People who are homeless. 

Other things that affect a person's risk for a heat-related illness during a heat wave include:

• Living in cities, because heat is trapped by tall buildings and air pollutants.
• Living alone.
• Not having cooling devices, such as fans or air-conditioning.