Observed Trends in Severe Weather Conditions Based on Humidex, Wind Chill, and Heavy Rainfall Events in Canada for 1953-2012

• Published in: Atmosphere-ocean Vol. 53; no. 4; pp. 383 - 397
• Main Authors: Mekis, Éva, Vincent, Lucie A., Shephard, Mark W., Zhang, Xuebin
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 08.08.2015
• Subjects: climate change; heavy rain; humidex; public alerts; severe weather conditions; urban centres; wind chill
• ISSN: 0705-5900; 1480-9214
• DOI: 10.1080/07055900.2015.1086970

Observed trends in severe weather conditions based on public alert statements issued by Environment Canada are examined for Canada. Changes in extreme heat and extreme cold events represented by various humidex and wind chill indices are analyzed for 1953-2012 at 126 climatological stations. Changes in heavy rainfall events based on rainfall amounts provided by tipping bucket rainfall gauges are analyzed for 1960-2012 at 285 stations. The results show that extreme heat events, defined as days with at least one hourly humidex value above 30, have increased significantly at more than 36% of the stations, most of which are located south of 55°N; days with nighttime hourly humidex values remaining above 20 have increased significantly at more than 52% of the stations, most of which are located south of 50°N. Extreme cold events represented by days with at least one hourly wind chill value below −30 have decreased significantly at more than 76% of the stations across the country. No consistent changes were found in heavy rainfall events. Because city residents are very vulnerable to severe weather events, detailed results on changes in extreme heat, extreme cold, and heavy rainfall events are also provided for ten urban centres.