Ottawa's medical officer of health has issued a heat warning for Friday and Saturday.

Heat warnings are declared when Environment Canada forecasts a humidex of 40 or more for at least two consecutive days.

The news comes as drought conditions in the Rideau Valley watershed continue due to low levels of rainfall in recent months.

The city warns that infants, young children, the homeless, and people taking medications such as anti-Parkinsons and antidepressants are at greater risk from extreme heat.

To avoid heat-related illness, people are advised to:

• Drink plenty of fluids, preferably water, and to avoid caffeine and alcohol
• Avoid strenuous outdoor physical activity
• Avoid direct exposure to the sun and seek shade and shelter at the first signs of heat exposure
• Wear lightweight and loose clothing
• Spend at least two hours a day in an air-conditioned location, including shopping malls, libraries or neighbourhood community centres
• Never leave children, the elderly or pets unattended in a car, even with the windows partly rolled down

High air pollution and UV index levels often occur during hot weather conditions.

An hourly air quality health index is available at airhealth.ca or by calling 1-866-688-3810.