3.1 Trends in observed seasonal weather compared to normal

Last Updated: 
July 2015


This indicator tracks the differences, called 'departures', in temperature from normal values measured for each season. The five-year moving average trend is also shown.

Normal values are the average observed temperatures and precipitation from 1961-1990. Departures are differences from this normal measured in degree Celsius for temperatures and in % for precipitation1. Seasons are defined as spring (March, April, May), summer (June, July, August), fall (September, October, November) and winter (December, January, February)1

The information is organized in two climate regions: the Mackenzie District including all forested NWT; and, the Arctic Tundra covering all tundra ecozones in the NWT as well as most of Nunavut and northern Quebec1.

Canadian Climate Regions - map
Canadian Climatic Regions – Forested NWT is called the Mackenzie District and NWT’s Arctic is included in the larger Arctic Tundra region. Map courtesy of © Environment Canada, Climate Research Division.

Information for this indicator is obtained from the Climate Trends and Variations Bulletin published every season by the Climate Research Division of Environment Canada1. Interpretation of climate trends are provided by the Climate Research Division, based on a study2 produced for Canada's Ecosystems Status and Trends Report. Quotes from the report and from the web-based Bulletin were noted. Additional interpretation specific to each graph for NWT was provided by Environment and Natural Resources, GNWT. 

NWT focus

This indicator presents a series of snapshots of NWT’s seasonal weather and compares it to what was measured as normal (average) between 1961-1990. Some weather events or large departures from normal can be used to analyze weather effects on wildlife, habitat disturbances, such as fires or floods, and the ability of people to travel or use renewable resources. The variable weather and extreme climate of the NWT are part of our environment. This indicator tells us how this variability is changing or becoming unpredictable.

Current view: status and trend


Temperature departures from normal vary greatly between years in the NWT (see NATURAL CLIMATE FLUCTUATIONS). In addition to these large fluctuations, temperatures during the past 15 years have been generally warmer in all seasons than during the 1961-1990. The warmest summer on record for both the Mackenzie District and the Arctic Tundra was during the strong El Niño event in 1998.

Warming temperatures are most notable in winter in both the Mackenzie District and the Arctic Tundra regions. The warmest winter ever recorded in the Mackenzie District was in 2005/2006 and in 2009/2010 in the Arctic Tundra3. Normal climatic variations could not explain these warm winters. For example,  no El Niño events occurred during these years (see NATURAL CLIMATE FLUCTUATIONS).

The Inuvialuit people have noticed ‘higher temperature and winter lows not as extreme” in the Inuvialuit Settlement Area3, Southern and Northern Arctic.


Spring temperatures are variable with a trend towards warmer weather and more variability during the last 15 years in both the Mackenzie District and the Arctic Tundra. The warmest spring on record across the NWT was in 2010.

Spring temperatures, NWT


Summers, in general, have shifted to slightly warmer than normal temperatures during the past 20 years in both the Mackenzie District and the Arctic Tundra.

Summer temperature, NWT


Fall temperatures are highly variable but, in general, have been warmer than normal for the past 20 years in both the Mackenzie District and the Arctic Tundra.

Fall temperature, NWT


Highest increase in winter temperature in all of Canada is occuring in the Mackenzie District. The temperature increased by 4.5ºC between 1948 and 2011. Overall, there is trend towards warmer winters in the Arctic Tundra for the past 20 years.

Winter temperature, NWT


Precipitation varies greatly between years across NWT’s climatic regions. The greatest departures from norm occurred during winter in the Arctic Tundra, where snowfall has increased by about 20-40%. This snow may not remain on the ground of as long as befor. The Inuvialuit  have noticed  precipitation is harder to predict and have noted there is less snow on the ground, which  doesn't last as long. They have also noticed more freezing rain in the winter in the Southern Arctic (Inuvik and Paulatuk)3.

Precipitation in the Mackenzie District is highly variable (see NATURAL CLIMATE FLUCTUATIONS). In contrast to the Arctic Tundra, winter snowfall in the Mackenzie District appears more variable with some declines in the past 20 years. This fits with climate change models predictions (see THE BIG PICTURE: A CHANGING PLANET).


Spring has been wetter than normal during 25 of the past 30 years but  drier during  drier for the past five years. 

Spring precipitation, NWT


Summer precipitation is highly variable in both the Mackenzie District and the Arctic Tundra.

Summer rain, NWT


Fall rain and snow in the Mackenzie District is highly variable but near normal. Fall 2013 was the third driest on record. 

Fall rain and snow, NWT


Snowfall in the Mackenzie District is highly variable. In 2013, the Mackenzie District had its driest winter on record at 37% drier than the baseline average. Snowfall in the Arctic Tundra is increasing noticeably, except during the past three years.

Winter snow, NWT

Canada snowfall map
Although snowfall is increasing across the Arctic Tundra climatic zone, regional differences can be significant. For example, although snowfall for that zone was average in Winter 2011-12, there were large differences in departures in the western and eastern Arctic. Snowfall in Winter 2011-12 was very low in northern NWT, but high in most of Nunavut. Source: Climate Research Division. Environment Canada1.

Looking forward

Both climate regions of the NWT are warming up. This is occurring in addition to the normal large annual and decade fluctuations in weather. Exceptionally warm winters, like 2005/06, should be expected in the future. Observed changes in both temperature and precipitation in the NWT have been larger than what is expected from natural climate variations and are consistent with predictions of climate changes due to increased greenhouse gas emissions4,5.

Snow in the the Arctic Tundra is increasing in winter. In addition, precipitation (wet snow or freezing rain) in both fall and spring has increased in the Arctic Tundra. Snow accumulation in the region is normally very small. For example, normal snow depth in Sachs Harbour, NT is only 8-14 cm6. It’s important to monitor changes in precipitation because rain or snow in fall or spring have been linked to increased mortality in Peary Caribou and muskox populations on the High Arctic islands (see SPECIES AT RISK). More variable and unpredictable weather is a serious concern for all Inuvialuit communities4.

Looking around

Trends in temperatures in winter from 1950-2007 - Canada
Trends in temperatures in winter from 1950-2007. Source: Climate Research Division of Environment Canada.

The strongest winter warming has occurred in western Canada, in particular in the Taiga Plains. The increase in winter temperature in the North is so pronounced, it drives national averages. These increases fit with model predictions of global climate changes due to human emissions of greenhouse gases16.

Technical note

The reference normals were estimated for the period 1951-1980 in the SOE report in 2009 and 2010. These were revised by the CRD to 1961-1990, the standard used by the World Meteorological Organization. Temperature and precipitation data have been re-calculated starting with the winter 2010-2011 Bulletin. There have been several changes to the data which, in some cases, changes the results of the calculations. First, more stations are used for the analysis (from 131 stations for the old CTVB to 470 stations in the new version for precipitation). Second, the reference period has changed. Third, adjustments for precipitation measurement errors is improved, as well as homogenization procedure for temperature. Fourth, a statistical procedure called "gridding" was applied to station values to get a more even representation for regional values. Technical note is from Environment Canada.

For more information

  • For more information on seasonal trends in the NWT and elsewhere in Canada, go to Climate Trends and Variations Bulletin published every season by the Climate Research Division of Environment Canada.

Other focal points

Contact us

Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.


Ref. 1 - Climate Research Division. 2015. Climate Trends and Variation Bulletin. Environment Canada.

Ref. 2 - Federal, Provincial, and Territorial Governments. 2010. Canadian Biodiversity: Ecosystem Status and Trends 2010

Ref 3 - Communities of Aklavik et al. 2005. Unikkaaqatigiit – Putting the Human Face on Climate Change: Perspectives from the Inuvialuit Settlement Region. Joint publication of Inuit Tapiriit Kanatami, Nasivvik Centre for Inuit Health and Changing Environments at Université Laval and the Ajunnginiq Centre at the National Aboriginal Health Organization. Ottawa. 

Ref. 4 - Min, S.K., X. Zhang, and E. Zwiers. 2008. Human-induced Arctic Moisturing. Science 320:518-520.

Ref. 5 - Zhang, X. et al. 2008. Canadian Climate Trends Ecosystem Status and Trends Report. Climate Research Division. Environment Canada.

Ref. 6 - Environment Canada. 2008. Climate Change Normals 1971-2000 - Sachs Harbour, NWT. Climate Normals & Averages. Canadian Daily Climate Data (CDCD).

Ref 7 - http://www.cbc.ca/news/canada/north/water-levels-dropping-in-n-w-t-due-t...

Ref 8 - Muir, AK. Arctic Resource Development and Climate Impacts. Adaptation and Mitigation Project Initial Summery of Climate Impacts and Adaptation for Energy. Mining and Infrastructure in Canada's North.

Ref. 9 - ENR. 2008. NWT climate change impacts and adaptation report