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The Climate of Yellowknife, Northwest Territories: What is the Typical Weather Like?

Welcome to the Yellowknife climate guide! Being the capital of the Northwest Territories in Canada, Yellowknife is known for its subarctic climate, marked by very cold winters and mild to warm summers. In this article, we will delve into the geographical factors influencing Yellowknife’s climate, discuss the typical weather you can expect, examine seasonal variations, and explore extreme conditions.

The climate of Yellowknife: A subarctic climate

Located at 62.45 degrees north, Yellowknife’s climate is largely influenced by its northerly position, the enormous landmass surrounding it, and a mountain range to the west causing Yellowknife to be in its rainshadow. The region falls within the extensive discontinuous permafrost zone, where frozen ground underlies 50 to 90% of the land due to the cold climate.

As a result, Yellowknife experiences extremely cold winters and mild to warm summers. The yearly average temperature is -4.3°C, earning it a subarctic classification under the Köppen climate system (Dfc).

Typical weather in Yellowknife

With an average frost-free period of just 115 days, Yellowknife has a short summer season. The average date of the last spring frost is May 25th, while the average date of the first fall frost is September 18th. Frost occurs on average on 224 days a year, with on 175 days a year the temperature not rising above 0°C at all. The area sees a yearly precipitation of a mere 288.6 mm, with July being the wettest month, boasting approximately 41 mm of precipitation. April is the driest month, with an average of only 5 days of precipitation, the majority being snowfall.

Yellowknife has the distinction of having the sunniest summer in Canada, averaging 1,034 hours from June to August. As testament to the severity of its winters, Environment Canada in 2014 ranked Yellowknife as having the coldest winter and longest snow cover season of any city in Canada, but also the sunniest spring and summer.

The snow cover, forming generally in October, remains permanent until late April. Snowfall can occur in every month of the year except July, although a snow cover has never formed in the summer months.

Climate table for climatological period 1981-2010 in Yellowknife, Northwest Territories, Canada.
Climate table for climatological period 1981 2010 in Yellowknife Northwest Territories Canada

Data source: Environment and Climate Change Canada Historical Climate Data website

Seasonal variation in Yellowknife: What weather to expect throughout the year

Yellowknife sees four seasons. However, their duration varies significantly. The winter season is particularly long, lasting 5 months, while the other seasons are rather short. For this reason, we deviate from the standard meteorological seasons to describe Yellowknife’s climate. 

Yellowknife winter climate (November-March): how cold does it get?

The winter in Yellowknife is notably harsh, with frost virtually every day and the majority of days experiencing minimum temperatures below -20°C. Regular temperatures below -30°C are also not uncommon. Even during the daytime temperatures can stay well below -20°C. January, with a mean temperature of -25.6°C, is the coldest month. The lowest winter temperatures in Yellowknife generally reach just under -40°C, with -51.2°C being the lowest ever recorded.

Due to the extremely cold weather, the atmosphere is rather dry, especially in the coldest winter months. Therefore, precipitation is limited. Precipitation almost exclusively falls as snow. The largest amounts of snowfall occur at the beginning of winter, e.g. November sees on average 36.5 cm of total snowfall. As the snowfall accumulates over the winter, snow depth is generally highest at the end of winter, in late February and March.

Besides cold, the winters are also very dark with just under 5 hours of daylight during the shortest days in December. However, in wintertime the Northern Lights regularly light up the sky. According to Yellowknife.com, Yellowknife is the best place in the world to view the Aurora Borealis, and the Northern Lights are visible almost every cloud-free night.

Yellowknife spring climate (April-May): Warming up after long winter

In April, frost still occurs on the majority of days. However, during daytime, the temperature starts rising above 0°C on a regular basis. With the average daily minimum temperatures still below -10°C, many people will nevertheless still experience April as a winter month. With the average maximum temperature slightly above 0°C, the region experiences a quick warm-up from late April onwards. The permanent snow cover generally lasts until the end of this month, but occasionally a snow cover forms even in May.

While May is generally a spring month in Yellowknife, frost still commonly occurs. At the same time, May is the month where daily maximum temperatures reaches above +10°C regularly and generally the first day(s) with temperatures above 20°C occur (at the end of) this month.

Yellowknife summer climate (June-August): sunny and mild to warm

Summers in Yellowknife are sunny and range from mild to warm, with temperatures often surpassing 20°C. July, with an average daily maximum of 21.3°C, is the warmest month of the year. The region experiences the sunniest summer in Canada during these months, and heatwaves can occur due to land climate characteristics and the large landmass to the south.

While it’s very sunny, the summer is the wettest season – but still not very wet – with about 110 mm precipitation over the 3 summer months. Where in the other seasons precipitation is mainly caused by frontal precipitation, in late spring and summer precipitation is mainly caused by rain showers and sometimes thunderstorms.

The summer days are long, with in June a daylight period of almost 20 hours. The sun first sets after 23:30, and even after sunset it doesn’t really get dark, as the sun hides just below the horizon. Due to the twilight occurring during the late spring and summer nights, northern lights cannot be seen this time of year.

Yellowknife autumn climate (September-October): Rapid temperature drop and onset of winter

With days swiftly getting shorter and the aurora’s returning during the increasingly long and dark nights, temperatures in Yellowknife start to decline rapidly, with the first frost typically happening in September. October sees the first ice days, when maximum temperatures drop below 0°C, indicating the onset of winter.

Fall is the season with most precipitation after summer in Yellowknife and as the fall progresses, the precipitation increasingly often falls as snow, with permanent snow cover generally starting in October.

Extreme weather in Yellowknife

Yellowknife has experienced many extreme weather conditions in its history. The lowest temperature ever recorded was an icy -51.2°C on January 31, 1947 and February 1, 1947. In contrast, the highest temperature on record was a hot 32.6°C on August 2, 2021. The highest wind chill was a chilling -64°C measured on January 29, 1971. The most snowfall in one day occurred on February 20, 1982, with 23.7 cm, while the highest amount of daily precipitation was recorded on August 15, 1973, with 82.8 mm.

Climate change in Yellowknife – Increasing wildfire risk?

With the worldwide climate warming, Yellowknife will see profound impacts of global warming, too. The snow cover season will be shorter, there will be less very cold days and summers will become warmer. The frost-free period will increase with several tens of days. All this will contribute to a shorter-lasting ice coverage on the Great Slave Lake.

Since warmer air generally contains more water vapor, the total amount of precipitation will increase, leading to more intense thunderstorms in summer and potentially more snowfall in winter. Simultaneously, the risk for extensive periods of heat and drought rises, leading to an increased wildfire risk.

Conclusion: prepare for Yellowknife’s extreme weather

In conclusion, Yellowknife’s climate, with its bitterly cold winters and warm, sunny summers, is a unique blend of extremes. Understanding the weather and climate in Yellowknife is vital in order to help visitors and residents prepare for life in this remarkable region. A lack of awareness of this extreme climate can cause dangerous situations. Always remember to check the weather forecast before you travel or plan outdoor activities in Yellowknife.

Read more:

What is climate & climatology?

Climate info for geographical regions

References:

  1. Köppen, W. and Geiger, R. eds., 1930. Handbuch der klimatologie (Vol. 1). Berlin: Gebrüder Borntraeger.
  2. Crameri, F. (2018), Scientific colour maps, Zenodo, doi:10.5281/zenodo.1243862
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