Montrealers may well be on their way to sweltering through their first heat wave of the year as temperatures this week are expected to continually break the 30C mark until this weekend.

Environment Canada is forecasting a high of 30 for Tuesday, 31 for Wednesday, and 32 on Thursday and Friday while nighttime temperatures will hover between 18 and 22.

Relief is expected on Saturday with the arrival of a cold front.

Meteorologists define a heat wave as three consecutive days during which the temperature does not fall below 30C and nighttime temperatures remain above 20C.

Humidex factors — a measure that takes into account the combined air temperature and humidity — also contribute to the calculation and are expected to jump this week as well.

“So long as we stay in the same air mass, we’ll be stuck with high humidex readings of 35 to 40C,” said André Cantin of Environment Canada, adding that the heat wave seemed to be centred on the greater Montreal area.

During periods of extreme heat, public health officials recommend that stays outdoors be broken up by several hours of exposure to a cooler environment, that physical activity be limited and water be consumed on a regular basis.

Last year, at least 66 persons died during a heat wave that gripped Montreal Island from June 30 to July 8. Most of the victims were elderly or suffered from chronic health problems.