Montreal's Heat Wave Action Plan

High Heat and Humidity Put Some Montrealers at Risk for Heat Stroke or Worse

Central Canada has been suffering from the heat for days, and with temperatures now reaching the mid-30s and the humidex (humidity index) tipping over 40ºC (104ºF) the city of Montreal is taking action to prevent heat-related illness and deaths.

Defining a heat wave

The American Meteorological Society defines a heat wave as a "period of abnormally and uncomfortably hot and usually humid weather." A standard application of that definition is a period of at least three days where heat reaches or exceeds 32ºC, but because weather patterns vary from one country or region to another, standards for an official heat wave will also vary. Quebec has a definition that uses a 30ºC minimum temperature, which means Montreal's heat wave started some days ago.

Health risks associated with heat waves

Anyone can suffer from heat stroke during weather extremes such as we are currently experiencing in central Canada at the moment, but certain people have an elevated risk and should take extra precautions. The elderly, children under age 5, and people suffering from any chronic cardiac or respiratory condition including asthma are in the population at elevated risk. Also a concern are people who spend a lot of time out in the sun: those who work outdoors, the homeless, and athletes who spend time training or competing outdoors. Even adolescents can be at risk, as they tend to be active outdoors.

People who take certain medications may be at elevated risk for sun burn during a heat wave, or may be more susceptible to heat stroke. The high heat and humidity can aggravate existing conditions such as high blood pressure or asthma. It can also result in fatigue or dehydration, or in heat stroke. Smog warnings should also be taken into consideration when evaluating risk levels.

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Image: Kilom691 (Wikimedia Commons)

Heat Wave Survival Tips

Avoid the summer sun during peak hours
Most of us realize the sun's effects are strongest around noon, but do really know what "peak hours" are? The Canadian Dermatology Association defines it as the time from 11 am to 4 pm. When ultraviolet readings are high (UV index 6-7) you should reduce exposure to the sun during this time, and take full precautions by wearing sunscreen, a shirt and a wide-brimmed hat. If the UV index reading is very high (8-10) or extreme (11+) it is best to avoid the sun as much as possible from 11 am to 4 pm. Remember, UV readings can be high even if the heat or sun don't seem strong!

Slip, Slop and Slap!
Never leave home without your protection, especially in summer's heat! Even when the UV reading is moderate (UV index 3-5) everyone should wear protection if they expect to be outside for more than 30 minutes. Slip on a shirt, slip on some sunscreen, and slap on a hat! Remember that sunscreen or sunblock are not intended to be your only protection against the sun: it's just one of the tools you should be using every day. Apply according to the label - that means using roughly enough to fill a shot glass, giving it 20 to 30 minutes to absorb into your skin before heading out the door, and re-applying as needed. Even on moderate UV days, seek shade at noon. Bringing along a bottle of water when you step out won't hurt, either.

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