As Montreal entered the second day of a four-day stretch when temperatures will hit more than 30 C the city announced it will take steps if necessary to keep people cool and safe.

Environment Canada triggered a heat warning for Montreal's core and for Laval, Longueuil, Chateauguay, and Gatineau on Wednesday morning, saying the heat and humidity are high enough that people could get heat stroke or heat exhaustion.

However it is not hot enough for Montreal to declare a heat emergency: that normally requires highs of 33 C for three days in a row.

Friday is expected to be the muggiest day of the week with humidity making it feel like 39 C although the actual temperature will be 31 C.

Overnight temperatures will be around 19 to 22 C until Saturday, at which point the heat and humidity will start to decline.

Other municipalities are also taking steps to help people keep cool, such as Ste. Anne de Bellevue, which has opened its pool and library until 5 p.m., and is keeping the Harpell Centre open until 10 p.m.

Heading to the beach may be an option, but not in Oka: that beach was closed earlier this week due to contamination.

The new Verdun beach is open, although signs saying the beach was closed were left up by mistake on Tuesday.

For now Montreal is encouraging people to drink plenty of water, to stay indoors in cool locations, and to reduce physical activity.

The city is also asking people to check on elderly or sick neighbours.

In the event of a heat emergency pools will be open longer, people without air conditioning at home will be encouraged to visit buildings where the climate is controlled, and health workers will expect to deal with more calls than usual.

Public Health, the fire department, and other agencies are making maps of where people at risk live or frequent so they can check on people during extreme heat.

"In the process of identifying vulnerable places we have included housing services because a) they have inspectors that are in the field, people that know places, that have firsthand knowledge and b) they developed a map or risk of inadequate housing conditions -- so that's in the Open Data, it's accessible to everyone -- and it's based on characteristics of the housing that we think are also probably at risk for heat exposures," said Dr. David Kaiser of the public health department.

This heat wave will be short, so is unlikely to have long-term effects on people's health.

At least 66 people died from June 30 to July 8, 2018 as a result of the heat wave on Montreal Island, while dozens more died throughout the province.

Two-thirds of those who died in Montreal were over the age of 65, and 73 percent suffered from a chronic illness.

June was slightly cooler and wetter than usual, and marked the ninth consecutive month with lower than average temperatures.

Normal temperatures for this time of year in Montreal are highs of 26 C and lows of 15 C.

Heat map shows Quebec's hot spots

What are the hottest spots in Quebec – and where can you find a dose of urban freshness?

The Quebec government created a surface temperature map in 2015 as part of its 2005-2012 Action Plan on Climate Change.

- With files from Kelly Greig