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Middlesex-London Health Unit

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Hot and Humid Weather Expected for the Next Three Days Prompting Heat Warning

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A forecast calling for three consecutive days of hot and hazy summer weather has led forecasters at Environment Canada to issue a Heat Warning for London and Middlesex County. The Middlesex-London Health Unit is using this as an opportunity to remind the public to take steps to stay cool and to keep hydrated as summer temperatures climb. The Heat Warning is expected to come into effect on Wednesday, July 26th and to be lifted overnight on Friday, July 28th, when the overnight low is expected to fall to 20°C. The current Environment Canada forecast calls for a three-day temperature spike with tomorrow’s daytime high expected to reach 30ºC with a humidex value of 37; similar conditions are expected for Thursday, while Friday’s high is expected to reach 32ºC.

Heat Warnings are issued when one or more of the following criteria are met:

  • Environment Canada issues a forecast calling for a daytime high of 31º Celsius or higher and a forecast low of 20º Celsius or higher for two consecutive days, or;
  • Environment Canada issues a forecast calling for a Humidex of 40º Celsius or higher for two consecutive days, or;
  • Environment Canada Forecasters anticipate that actual temperatures and humidex values in London and Middlesex County will reach the thresholds noted above.

The Health Unit recommends the following tips to avoid the risks of heat-related illness:

  • Drink plenty of water and natural juices throughout the day, even if you don't feel very thirsty.
  • Never leave a child or pet in a parked car or sleeping outside in direct sunlight.
  • Avoid drinking alcoholic beverages, as well as coffee and cola.
  • When possible, avoid spending too much time outdoors. If you must be outside, seek shade as much as possible. Plan outdoor activities in the early morning or evening.
  • Wear a wide-brimmed hat when outdoors.
  • Keep shades or drapes drawn and blinds closed on the sunny side of your home.
  • Avoid turning on electric lights in your home.
  • Take a cool bath or shower periodically or cool down with cool, wet towels.
  • Avoid eating heavy meals and using your oven.
  • Avoid intense or moderately intense physical activity.
  • Use fans to draw cool air at night, but do not rely on a fan as a primary cooling device during extended periods of excessive heat.
  • Reduce the use of personal vehicles, stop unnecessary idling; avoid using oil-based paints and glues, pesticides, and gas-powered small engines.

Visit: for more information on heat-related illness.

Media Contact:
Morgan Lobzun, Communications Coordinator, Middlesex-London Health Unit,
519-617-0571 (cell.)

David Pavletic, Food Safety & Healthy Environments Manager, Middlesex-London
Health Unit

Tags: Heat Warning