A multi-day heat event is expected in southern Ontario beginning on Monday.
Over the course of three days, daytime highs near 30 degrees are expected and overnight lows will be about 20 degrees.
In the daytime, humidex values may reach 36 to 38.
Conditions will improve on Thursday.
While extreme heat can put everyone at risk from heat illnesses, health risks are greatest for older adults, infants and young children, people with chronic illnesses (like breathing problems, mental illness, and heart problems), people who work in the heat, people who exercise in the heat, homeless people, and low-income earners.
In extreme southwestern Ontario, heat warnings are issued when 2 or more consecutive days of daytime maximum temperatures are expected to reach 31°C or warmer and nighttime minimum temperatures are expected to fall to 21°C or warmer. Or, when 2 or more consecutive days of humidex values are expected to reach 42 or higher.