Environment Canada has issued a heat warning for Montreal ahead of expected humidex values reaching and maybe even exceeding 40. The federal weather agency says this high-heat, high-humidity combo could last through the weekend.

The warning covers much of southern Quebec, from Estrie to Mauricie, Montreal and surrounding regions, and Outaouais.

Montreal's Friday forecast shows actual temperatures peaking at 28 C in the late afternoon but humidex values reaching between 35 and 36 between 3 p.m. and 6 p.m.

The forecast for Saturday and Sunday shows temps reaching 33 C and 31 C, respectively. The Weather Network predicts the humidex will reach 41 by Saturday afternoon.

Environment Canada says it issues such warnings when "very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion."

The agency encourages residents to drink water regularly and avoid outdoor activities during times of the day when the temperature is highest.