Climate Trends and Variations Bulletin - Summer 2013
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.
The national average temperature for the summer of 2013 (June, July and August) was 0.9°C above baseline average (defined as the mean over the 1961-1990 reference period), based on preliminary data, which makes this past summer the 8th warmest observed since nationwide recording began in 1948. The warmest summer on record occurred in 2012 when the national average temperature was 1.8°C above the baseline average. The coolest summer occurred in 1978 when temperature averaged across the county was 1°C below the baseline average. The temperature departures map for the summer of 2013 (below) shows that near normal temperatures were experienced across much of south-central and eastern Canada. Stronger positive temperature departures occurred over B.C. and northwestern Canada. The strongest negative temperature departures were recorded for Ellesmere Island and the far North.
Temperature Departures from the 1961-1990 average - Summer 2013
The time series graph below shows that, when averaged across the nation, summer temperatures have fluctuated from year to year over the period 1948-2013. The red dashed linear trend line indicates that summer temperatures have warmed by 1.3°C over the past 66 years.
Summer National Temperature Departures and long-term Trend, 1948 - 2013
When examined on a regional basis, only the Arctic Mountains and Fiords region recorded summer temperatures below the baseline average in the summer of 2013 (17th coolest, 0.2°C below the baseline average). Positive temperature departures occurred in the remaining regions and were most pronounced in the Yukon/North B.C. Mountains (2.0°C above baseline average, 2nd warmest summer), the Mackenzie District (1.9°C above baseline average, 5th warmest summer) and the South B.C. Mountains (1.5°C above baseline average, 5th warmest summer). Summer temperatures in the Northwestern Forest and Pacific Coast regions were both 1.2°C above baseline in 2013 (ranked 6th and 7th warmest in these regions since 1948 respectively). All eleven climate regions exhibit positive trends in summer temperatures over the 66 years of record. The strongest trend in regional summer temperatures is observed in the Mackenzie District (1.7°C) while the weakest trend is observed for the Prairies (0.8°C). A table listing the regional and national temperature departures and rankings from 1948 and a table that summarizes regional and national trends and extremes are available on request to CTVB@ec.gc.ca.
As a whole, Canada experienced a slightly wetter than average summer in 2013 (3% above the baseline average) making it the 25th wettest summer observed over the 66 years of record. Over the period of record, the wettest summer was 2005 (15% above the baseline average) and the driest was 1958 (14% below the baseline average). The precipitation percent departure map for summer 2013 (below) shows notably drier than average conditions for much of central B.C. and Alberta, northern Saskatchewan and Manitoba, southeastern Nunavut, southern Baffin Island, northwestern Quebec and Newfoundland. A wetter than average summer was experienced in central Saskatchewan and Manitoba, across much of eastern Ontario, the Maritimes and, most notably, in the far north.
Precipitation Departures from the 1961-1990 average - Summer 2013
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 9-year Running Mean, 1948-2013
The summer of 2013 was the wettest on record (i.e. from 1948-2013) for the Arctic Mountains and Fiords region (56% above the baseline average). The only other region that recorded summer precipitation notably greater than the 1961-1990 average was the Great Lakes/St. Lawrence Lowlands region (19% above baseline). The driest regions in the summer of 2013 were the South B.C. Mountains (20th driest summer since 1948, 9% below the baseline average) and the northwestern Forest region (23rd driest summer, 5% below the baseline average). A table listing the regional and national precipitation departures and rankings from 1948 and a table that summarizes regional and national extremes are available on request to CTVB@ec.gc.ca.
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