MHLU - Health Status Resource

Extreme Weather Conditions

Extreme Weather Conditions

Key Findings: 
  • The annual number of extreme temperature alerts over time has varied however the total indicates that Middlesex-London experienced more cold alerts (and total days under cold alert) than heat alerts (Fig. 11.9).
  • 2009 was particularly cold, with eight separate alerts over a total of 20 days (Fig. 11.9). 
  • 2005 and 2010 had the highest number of heat alerts and days under alert for the whole time period (Fig. 11.9).
Interpretive Notes

Extreme Temperature Alerts are issued by the Middlesex-London Health Unit to inform local agencies, stakeholders and the media of a forecast of extreme weather temperatures to ensure that the homeless and other vulnerable persons are protected during these times of extreme temperature. The alert system allows for the notification to be done in a coordinated and preventative manner.

Criteria for Initiating Alerts

  1. A Heat Alert (full alert to the agencies, stakeholders and the media) is initiated in the following circumstances, when one or more of these criteria are met:
    • The forecast is showing a humidex value of 40 or higher; or
    • The humidex is forecast to rise to 36 or higher, combined with an Environment Canada Smog Alert; or
    • Environment Canada issues a humidex warning for outdoor activity for people in the Middlesex-London area; or
    • High temperatures, without a humidex warning, equal 38o Celsius or above.
  2. A Cold Alert (full alert to the agencies, stakeholders and the media) is initiated in the following circumstances, when one or more of these criteria are met:
    • Daily predicted low temperature of –15o Celsius without wind chill; or
    • The wind chill reaches the level at which Environment Canada issues a warning for outdoor activity for people in the Middlesex-London area; or
    • Extreme weather conditions, such as a blizzard or ice storm.
Ontario Public Health Standard: 

Population Health Assessment and Surveillance Protocol - Section 1, Subsections b-iii, vi, viii

Rabies Prevention Control - Requirement #4

Infectious Diseases Prevention and Control Standard - Requirement #3

Health Hazard Prevention and Management Standard - Requirement #2