A data-driven approach to setting trigger temperatures for heat health emergencies

Area of Science:

• Environmental Health
• Public Health
• Climate Change Adaptation

Background:

• The summer of 2009 saw unprecedented heatwaves in Greater Vancouver, Canada, leading to significant excess mortality.
• Public health authorities require evidence-based recommendations for heat-health emergency action plans to mitigate future risks.

Purpose of the Study:

• To establish a specific temperature threshold for triggering heat health emergency action plans in Greater Vancouver.
• To develop a rapid, evidence-based recommendation to reduce potentially avoidable mortality during extreme heat events.

Main Methods:

• Analyzed historical data (2005-2009) correlating extreme mortality days with extreme temperature days from two regional airports.
• Defined historical heat health emergencies based on coinciding extreme temperature and mortality days.
• Retrospectively tested early warning scenarios using forecast and observed temperatures to predict these events.

Main Results:

• Extreme mortality correlated with a 2-day average maximum temperature of ≥31°C (coastal) and ≥36°C (inland).
• All historical heat health emergencies were identified in 4 out of 12 scenarios, with a minimum of two false positives.
• The proposed trigger identified historical events with a lead time of 19 hours.

Conclusions:

• Recommend triggering a heat health emergency for Greater Vancouver when the average of the current day's 14:00 observed temperature and the next day's forecast high reaches ≥29°C (coastal) or ≥34°C (inland).
• This threshold provides adequate lead time for emergency responders and stakeholders.
• The proposed trigger is clearly understood and actionable for public health preparedness.