Raincouver: A Legacy of BC’s Temperate Rainforest?

In Vancouver, BC’s most populous city, this unique temperate rainforest is often thought to be the reason behind our city's yearly average of 169 rain days and the nickname, Raincouver.

Wolf Read, a meteorologist and weather forecasting research assistant at the University of British Columbia explains that temperate rainforests help contribute water to the atmosphere during transpiration (when plants release water into the atmosphere as vapour during photosynthesis) and influences how much precipitation we receive. 

But our rainforest is just one reason behind the amount of rainfall we see every year in Vancouver. As Wolf points out, other factors such as the tilt of the Earth’s axis, energy from the sun, and Vancouver’s location on the northeast side of the Pacific Ocean are also to thank for our rainy city.

The Pacific Ocean and The Cascade Range 

Wolf, who teaches geography at Simon Fraser University, explains that winds travelling over the Pacific Ocean and heading towards shore picks up moisture as water evaporates off the ocean’s surface after it is heated by the sun. 

Being a large body of water, the Pacific Ocean does not heat or cool rapidly—it responds to seasonal changes slowly—and hangs on to energy that keeps our temperatures more moderate, giving us milder winters and cooler summers.  

As the moisture from the ocean moves over our mountains, namely The Cascades, it’s pushed upwards resulting in cooler air which does not support as much water vapour as warmer air. The water vapour that is lost as the air cools down, becomes rain. 

Energy from the Sun and Vancouver’s Latitude  

The sun is a mighty star. The role it plays on Earth is crucial to our well-being: it fortifies the plants that provide us with food and oxygen; warms our seas and atmosphere; and drives our weather patterns. The sun affects the movement of air, the formation of clouds, and the water cycle! 

Energy from the sun also heats up air at the equator, causing it to rise and head toward the poles where it cools down. 

Because of Vancouver’s latitude (we’re located mid-latitude, roughly half-way between the equator and the North Pole), the energy we receive from the sun is not as intense as the solar energy received in low-latitudes, which are closer to the equator and get more solar energy, leading to more heat.  

Our mid-latitude location means we have mild temperatures as well as large scale wind patterns from the west to southwest that bring abundant rain from off of the Pacific Ocean.

The Tilt of the Earth’s Axis 

The tilt of the Earth’s axis causes different parts of the globe to experience weather changes differently. In the winter months, we’re tilted away from the sun and get cooler temperatures. Wolf shares that this causes the North Pole, which is the northernmost point on the Earth, to be pointed away from the sun completely, resulting in even colder temperatures. 

“During this time there’s little solar energy warming the North Pole—it gets colder and colder. This strengthens the temperature difference between the equator and the poles. As the temperature difference increases, the winds get stronger in the mid-latitudes, bringing in more frequent storms.” 

Wolf adds that all of these rainy days in turn cause the lush rainforest—with its rich vegetation and evergreen shrubs—that we enjoy so much to flourish. “Whether we call it Raincouver, Wet Coast or as some even say, the Pacific North Wet, our temperate rainforest is also a product of this climate.” 

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Wanna experience all the seasons from inside a travelling backyard? 

Walk through all the seasons on a treadmill, practice growing a pumpkin in different weather conditions, and learn about the science in your own backyard in our current feature exhibition, Backyard Adventures presented by Windsor Plywood Foundation. On until January 2022.