Science Literacy Week 2020 is here! Click to read more.

Why is Vancouver so rainy?

Have you ever walked down Main Mall soaking wet with an umbrella in one hand and a muggy backpack in the other? Then you ask yourself why on earth you decided to study in Vancouver — a city with an average of 160 rainy days a year.

"Anytime we have the winds coming from a westerly direction ... the air is coming over the Pacific where it has picked up lots of water that has evaporated from the ocean. This humid air is coming towards to mountains.... As the air is forced to rise, the air cools, water vapour condenses and we get rain," explained Roland Stull, professor and director of the Geophysical Disaster Computational Fluid Dynamics Centre at UBC.

In the fall and winter, low weather pressure is known as a mid-latitude cyclone. These cyclones are storms that form on the Asian side of the Pacific and travel across the ocean. These storms become their strongest when they cross the international date line in the middle of the Pacific Ocean. Once they reach Vancouver, they are already decaying because of Vancouver’s strong, winter winds. Many of these storms go to the cold waters of Alaska where they lose energy and die out, leaving Vancouver with the clouds.

Stull also mentioned that it does not necessarily rain more in Vancouver than in other places in Canada. Rather, Vancouver has more days of rain in comparison to other places that have fewer days of rain, but have stronger rain in the form of storms.

Vancouver saw an average of 1457 millimetres of rain over 168 days from 1981 to 2010.