Environment Canada has issued a heat warning for Mississippi Mills, Ontario, as a prolonged heat wave is expected to grip the area through at least Saturday, July 4, 2026. The federal weather agency is warning of very hot conditions and advising residents to check on family, friends, and neighbours, especially those who live alone or are at higher risk.
As of Monday afternoon, the temperature hit 30.3°C with a humidex of 33 at the Ottawa airport weather station. The forecast for the rest of the week calls for highs of 29°C on Tuesday (with a 40 percent chance of showers and risk of a thunderstorm), 32°C on Canada Day Wednesday, and 33°C on both Thursday and Friday. Humidex values could make it feel as hot as 38, and a very high UV index of 8 is expected on Tuesday. Overnight lows will only drop to 21 to 23°C, offering little relief.
These conditions meet the criteria for a heat warning set by Southeast Public Health (formerly the Leeds, Grenville and Lanark District Health Unit). A heat warning is issued when daytime highs of 31°C or more and nighttime lows of 20°C or higher last for at least two days, or when the humidex reaches 40 for two days. Dr. Linna Li, Medical Officer of Health for Southeast Public Health, advises residents to stay cool and hydrated.
The Municipality of Mississippi Mills has opened four cooling centres for anyone needing a break from the heat. These are the John Levi Community Centre in Almonte, the Stewart Community Centre in Pakenham, and the Mississippi Mills Public Library branches in both Almonte and Pakenham. Those most at risk include the elderly, people with chronic illnesses, infants and young children, those with inadequate housing, and anyone doing strenuous outdoor work or exercise.
The heat wave coincides with Canada Day celebrations on July 1 at Gemmill Park in Almonte. Festivities will include live music, bouncy castles, face painting, and fireworks. Health officials remind attendees to take precautions, such as drinking plenty of water and seeking shade.
