Changes in precipitation

Average annual precipitation has increased across Canada. With continued climate change, future precipitation is expected to increase in some regions and seasons, but decrease in others.

Precipitation concepts

Precipitation is any form of water that falls from clouds and reaches the ground. Precipitation can be liquid or solid and includes rain, snow, freezing rain, hail and drizzle.

Precipitation is usually measured in millimetres (mm). Precipitation that falls as snow can be measured in centimetres (cm) and converted to water content in millimetres.

Change in precipitation refers to how precipitation has increased or decreased from a specific reference period. A reference period helps us measure change over time.

Patterns of precipitation change in Canada

Average (mean) annual precipitation increased in Canada from 1948 to 2012.  Northern Canada experienced the highest relative increase in precipitation. Significant increases in precipitation were also observed in parts of southern Canada, including eastern Manitoba, western and southern Ontario, and Atlantic Canada.

Future changes in precipitation are projected to vary depending on the region and season. This is unlike temperature, which is projected to increase everywhere in every season.

In the short-term, a small increase in precipitation is projected in all seasons, with larger increases in northeastern Canada. Over the second half of the 21st century, projected changes in precipitation are affected by emission scenario. Under a low emission scenario, small increases in precipitation are projected. Under a high emission scenario, a larger increase is projected in annual and winter precipitation. However, a small decrease is projected in summer precipitation over large areas of southern Canada.

The amount of extreme precipitation for a short-duration (a day or less) is projected to increase, with larger increase corresponding to stronger warming.

Find precipitation data in the library of climate resources.

Figure 1: Projected percentage change in annual precipitation from the 1986 to 2005 reference period. Changes are for the end of the century assuming a high global emission scenario.
Projected percentage change in annual precipitation from the 1986 to 2005 reference period. Changes are for the end of the century assuming a high global emission scenario

This figure is a map of projected changes in annual precipitation by the end of the 21st century across the Canadian landmass. Changes in precipitation are given as a percent change from the 1986-2005 reference period. The dataset used here is a statistically downscaled dataset, based on the Bias Correction/Constructed Analogues with Quantile mapping reordering (BCCAQ) version 2. The emission scenario used here is the Representative Concentration Pathway 8.5.

Long description

The colours on the map indicate the amount of projected change. Precipitation increases range from around 8% to over 70%. The largest increases are seen in northern regions, particularly over Elsmere Island where increases are over 70%. The smallest changes are seen in the Prairies as well as the southwest coast of British Columbia.

Impacts of precipitation change

Changes in precipitation, along with changes in temperature, can contribute to many impacts, including more frequent and severe floods and droughts.

Depending on where you live, flooding could result from:

  • more frequent and intense rainfalls, such as downpours from thunderstorms
  • more instances of rain falling on snow
  • new storm patterns

Flooding can overwhelm infrastructure and cause serious local impacts on life and livelihoods. It can impact transportation networks, disrupting access and supply chains, and contaminate water.

More frequent and intense droughts would decrease water availability and quality. Droughts can lead to increased water cost and competition for access to quality water for drinking, water-related activities and tourism. Droughts also have impacts on agriculture, ecosystems, and wildlife.

Even relatively small changes in precipitation patterns and amounts can have big impacts, especially if these changes persist over time. For example, some plants are very sensitive to changes in available moisture. Changing patterns and amounts of precipitation can result in large shifts in ecosystems over time.

Adapting to precipitation change

Canadians can take many different approaches to adapt to changing precipitation patterns, including for example:

  • municipalities can improve infrastructure to withstand changes in the frequency and intensity of extreme rain events
  • governments can restrict construction in flood plains
  • communities can prepare for potential increases in drought by adopting new technologies and water management methods, such as carefully managing natural drainage systems like wetlands to conserve water

Improving resiliency to droughts and floods requires collaboration between communities, governments, industry and researchers.

Sources
  • Environment and Climate Change Canada. 2017. Climate data and scenarios: synthesis of recent observation and modelling results. Government of Canada.
  • Government of Canada. 2018. Glossary. Government of Canada.
  • Warren, F. J, and Lemmen, D. S. 2014. Canada in a Changing Climate: Sector Perspectives on Impacts and Adaptation. Ottawa, ON: Government of Canada.
  • Zhang, X., Flato, G., Kirchmeier-Young, M., Vincent, L., Wan, H., Wang, X., Rong, R., Fyfe, J., Li, G., Kharin, V.V. 2018. Changes in Temperature and Precipitation Across Canada; Chapter 4 in Bush, E. and Lemmen, D.S. (Eds.) Canada’s Changing Climate Report. Ottawa, ON: Government of Canada.

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