Climate Trends and Variations Bulletin - Summer 2012
This bulletin summarizes recent climate data and presents it in a historical context. It first examines the national temperature, and then highlights interesting regional temperature information. Precipitation is examined in the same manner.
National Temperature
The national average temperature for the summer of 2012 was 1.9°C above normal (1961-1990 average), based on preliminary data, which makes this summer the warmest on record since nationwide records began in 1948. The previous record was held by 1998 with a temperature of 1.7°C above normal. At 1.0°C below normal, 1968 was the coolest. As the temperature departures map below shows, virtually all of the country was above normal this summer, with most of the Northwest Territories, northern Yukon, northern Quebec, and Labrador all experiencing temperatures at least 2.5 degrees above normal. The coastal areas of British Columbia through to the Yukon had temperatures closest to normal this summer.
Temperature Departures from Normal - Summer (June, July, August) 2012
The time series graph below shows that the last time the summer average temperatures was below normal was in 2004. The red dashed linear trend line indicates summer temperatures have warmed over the last 65 years by 1.4°C.
Summer National Temperature Departures and long-term Trend, 1948 - 2012
Regional Temperature
The summer of 2012 was ranked among the ten warmest summers since 1948 in 10 of the 11 climate regions. Record high summer temperatures were observed in three of the regions: Arctic Mountains and Fiords (2.5°C above normal); Northwestern Forest (1.8°C above normal); and Atlantic Canada (1.6°C above normal).
Summer 2012 temperatures were also among the warmest 10 summers on record for: Mackenzie District (2nd warmest, 2.5°C above normal); Arctic Tundra (2nd warmest, 2.3°C above normal); Northeast Forest (2nd warmest, 1.9°C above normal); Great Lakes/St. Lawrence (4th warmest, 1.5°C above normal); Prairies (7th warmest, 1.1°C above normal); North British Columbia/Yukon (7th warmest, 1.1°C above normal); and South British Columbia Mountains (10th warmest, 0.9°C above normal). The Pacific Coast was the one region that had a near normal summer, 0.2°C above normal and ranked 29th warmest. All the regional and national temperature departures and rankings are presented in the ranked regional temperatures table (MS Excel Version, 41 KB). The trends, extremes and current year rankings table shows that all eleven climate regions exhibit positive trends in summer temperatures over the 65 years of record. The greatest trend is observed in the Mackenzie District (1.6oC) while the weakest trend is observed for the Prairies region (0.9°C over the same period).
National Precipitation
As a whole, Canada experienced a wetter than normal summer in 2012 (4% above the 1961-90 normal). The summer of 2012 ranked as the 19th wettest out of the 65 years of record. Over the period of record the wettest summer was 2005 (15% above normal) and the driest was 1958 (14% below normal). The precipitation percent departure map for summer 2012 (below) shows wetter than normal conditions in southern B.C., Alberta, most of Saskatchewan, central Manitoba, Yukon, southern Northwest Territories, northern and eastern Nunavut, and northern Quebec. Drier than normal areas include, northern B.C., northern Northwest Territories, southern Manitoba, northern Ontario, southern Ontario and Quebec, Newfoundland and Labrador, and Nova Scotia.
Precipitation Departures from Normal - Summer (June, July, August) 2012
It should be noted that "normal" precipitation in northern Canada is generally much less than it is in southern Canada, and hence a percent departure in the north represents much less difference in actual precipitation than the same percentage in the south. The national precipitation rankings are therefore often skewed by the northern departures and do not represent rankings for the volume of water falling on the country.
The precipitation percent departures graph below shows that summers have tended to be wetter than normal since the mid-1970s.
Summer National Precipitation Departures with Weighted Running Mean, 1948 - 2012
Regional Precipitation
Precipitation departures varied substantially across the country in the summer of 2012. For example, the Arctic Mountains and Fiords climate region had its fourth wettest summer on record (30% above normal). While, on the other hand, Atlantic Canada had its 9th driest summer since 1948 (22% below normal). The national and regional precipitation departure values along with their rankings for the summer of 2012 relative to the last 65 years are listed in the ranked regional precipitation table (MS Excel Version, 44 KB). This past summer’s precipitation rankings for each region, along with the record wettest and driest years, are summarized in the extremes and current year rankings table.
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