Precipitation change in Canada

Changes in climate variables such as temperature, precipitation and humidity affect a wide range of natural processes and human activities. Globally, while annual average precipitation varies greatly from region to region, precipitation at land-based stations has been near the reference value^{Footnote [1]},^{Footnote [2]} for the third consecutive year. In 2014, global precipitation was 0.52 millimetres or 0.05% below the 1961-1990 reference value.

Annual average precipitation in Canada for the year 2014 was 2% below the 1961-1990 reference value.^{Footnote [3]} However, the climate tended to be wetter from the mid-1970s onward, as shown by an ever increasing nine-year moving average, with the wettest year being 2005, at 16% above the reference value. In contrast, Canada's driest year on record was 1956 at 12% below the reference value. Regional patterns vary greatly however (see Regional precipitation change).

Annual average precipitation departures from 1961-1990 reference value, Canada, 1948 to 2014

Note: Annual average precipitation departures were computed for weather stations across Canada with sufficiently long data records to allow for trend calculation and were then interpolated to a 50-kilometre spaced grid. Annual grid points values were averaged together to produce an annual time series of precipitation departures representing the entire country.
Source: Environment and Climate Change Canada (2015) Adjusted and Homogenized Canadian Climate Data (AHCCD).

Seasonal precipitation change

During the past 67 years (1948-2014), the seasonal average precipitation departures for Canada have shown an overall upward progression for each of the four seasons (as illustrated by the nine-year moving average lines in the charts below). All seasons tended to be wetter than the corresponding 1961-1990 reference value from the mid-1970s onward. The wettest winter recorded occurred in 2011,^{Footnote [4]} while the wettest spring, summer and fall were in 2012, 2005 and 2010, respectively. The driest seasons recorded were all in the 1950s (winter 1957, spring 1956, summer 1958 and fall 1952).

Seasonal average precipitation departures from the 1961-1990 reference value, Canada, 1948 to 2014

Note: Seasonal average precipitation departures were computed for weather stations across Canada with sufficiently long data records to allow for trend calculation and were then interpolated to a 50-kilometre spaced grid. Annual grid point values were averaged together to produce an annual time series of precipitation departures representing the entire country. Seasons are defined as winter (December of previous year, January and February), spring (March, April and May), summer (June, July and August) and fall (September, October, and November). The seasonal average precipitation departures for 2014 are based on preliminary data.
Source: Environment and Climate Change Canada (2015) Adjusted and Homogenized Canadian Climate Data (AHCCD).

Regional precipitation change

In 2014, while annual average precipitation in the country as a whole was 2% below the Canadian 1961-1990 reference value, southern Saskatchewan and some areas in Ontario had wetter conditions than the reference value while most of Yukon, Northwest Territories and part of Nunavut (Ellesmere Island) had drier conditions. The rest of the country had average precipitation departures near the reference value.

Regional average precipitation departures from 1961-1990 reference value, Canada, 2014

Note: Annual average precipitation departures were computed for 464 weather stations across Canada and were then interpolated to a 50-kilometre spaced grid.
Source: Environment and Climate Change Canada (2016) Canadian Gridded Temperature and Precipitation Anomalies (CANGRD).

Related indicators

• Temperature Change in Canada

Other information

• Environment and Climate Change Canada: Climate Trends and Variations Bulletin
• Environment and Climate Change Canada: Adjusted and Homogenized Canadian Climate Data (AHCCD)