Climate Trends and Variations Bulletin - Spring 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 spring of 2012 was 1.6°C above normal (1961-1990 average), based on preliminary data, which makes this spring the ninth warmest on record since nationwide records began in 1948. The warmest spring was in 2010, which was 4.1°C above normal. At 2.0°C below normal 1974 was the coolest. As the temperature departures map below shows, virtually all of the country was above normal this spring, with southern Manitoba, most of Ontario, and southern Quebec experiencing temperatures more than 3 degrees above normal. Small areas of the British Columbia coast, northern Yukon and western Northwest Territories had temperatures closest to normal this spring.
Temperature Departures from Normal - Spring (Mar, Apr, May) 2012
The time series graph below shows that spring temperatures have fluctuated greatly. The red dashed linear trend line indicates spring temperatures have warmed over the last 65 years by 1.8°C.
Spring National Temperature Departures and Long-term Trend, 1948 - 2012
Regional Temperature
Four climate regions experienced rankings among their ten warmest springs this year. They were: Great Lakes/St. Lawrence (2nd warmest, 3.5°C above normal); Atlantic Canada (4th warmest, 2.1°C above normal); Prairies (5th warmest, 2.3°C above normal); and Northeastern Forest (6th warmest, 2.5°C above normal). 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 of the eleven climate regions exhibit positive trends in spring temperatures, with the Mackenzie District and the Northwest Forest showing the greatest trends of 2.6°C over the 65 years of record. Arctic Mountains and Fiords Region has the least positive trend of 0.9°C over the same period.
National Precipitation
Canada experienced a slightly wetter than normal spring in 2012, 3% above normal (1961-1990 average). This spring ranked as the 24th wettest out of the 65 years of record. The wettest spring was 1979, 20% above normal, and the driest spring was 1956, 27% above normal. The precipitation percent departure map below shows most of country had wetter than normal conditions, with the Prairie Provinces, southern Yukon and Northwest Territories, and northern Ontario experiencing conditions that were at least 40% wetter than normal. Three areas of drier than normal conditions were Nunavut, southern Ontario, and Atlantic Canada.
Precipitation Departures from Normal - Spring (Mar, Apr, May) 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 a smaller change in the actual amount of precipitation than the same percentage in the south. The national precipitation rankings are therefore strongly influenced 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 springs have tended to be wetter than normal since the mid-1970s.
Spring National Precipitation Departures with Weighted Running Mean, 1948 - 2012
Regional Precipitation
Atlantic Canada climate region had its driest spring on record, 28% below normal, beating out 1959 at 25% below normal. One other region had a top ten driest spring: the Great Lakes/St. Lawrence Region had its 6th driest spring, 26% below normal. Three climate regions had one of their ten wettest springs this year: the Prairies (3rd wettest, 52% above normal); Northwestern Forest (7th wettest, 19% above normal); and North B.C. Mountains/Yukon (7th wettest, 18% above normal). The national and regional values along with their rankings for the spring of 2012 relative to the last 65 years are listed in the ranked regional precipitation table (MS Excel Version, 44 KB). This past spring’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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