Establishing Appropriate Hot Weather Alerting Criteria for British Columbia, Canada

摘要

A heat health warning system (HHWS) was developed for the greater Vancouver area of British Columbia (BC), Canada following an unprecedented extreme hot weather event that resulted in a 40% increase in weekly mortality. While the greater Vancouver HHWS has been operational since 2012, there are currently no HHWSs covering the remainder of the province. In collaboration with Environment and Climate Change Canada we established hot weather alerting criteria for four regions with broadly similar climates in BC. We used daily forecasted and observed minimum and maximum air temperatures and daily mortality counts for May through September during 2004 to 2016. For each date (dayt), we selected daytime forecast high temperatures for dayt and dayt+1 and the overnight forecast low temperature falling between dayt and dayt+1 from forecasts made in the afternoon of dayt-2. We tried a range of combinations of minimum and maximum temperature thresholds for each of four climatic areas. For each date, we assigned a hot weather warning category equal to the sum of the total degrees by which the daytime forecast highs fell under the maximum threshold and the overnight forecast low fell under the minimum threshold. We assessed associations between the categories and daily mortality using time-series models. We established the following minimum/maximum hot weather alerting criteria, to be adopted in the summer of 2018: 16°C/29°C in the Southwest; 18°C/35°C in the Southeast; 13*C/28°C in the Northwest; and 14°C/29°C in the Northeast. These values were established by balancing a number of considerations regarding the appropriateness of each threshold, including evidence-based associations with daily mortality and minimization of warning fatigue. These criteria identified the two province-wide extreme hot weather events that affected BC in 2009 and 2015. Hot weather alerting criteria covering all of BC can help public health authorities and citizens prepare for extreme hot weather events.