Fog as an Abiotic Factor at Race Rocks

fog in the Strait

Wikipedia lists 9 different types of fog. Race Rocks experiences precipitation fog in the winter and steam fog in the summer. Steam fog occurs when cold air passes over warmer water.

Precipitation fog occurs when clouds of water vapor begin to condense. When the temperature reaches the dew point, vapor condenses to leaves behind small droplets of water. Fog is therefore a source of moisture. See example below: Many animals and plants can survive on the moisture left behind by fog. In tropical areas fog has the greatest effect on the surrounding ecosystem, providing water crucial to the survival of many plants and animals. Fog data for Race Rocks has not been collected , but the precipitation from either steam or precipitation fog is often recorded as a 0.2mm entry on the weekly rain record . An example is shown below.

fogbankFrequently in the summer, the Strait of Juan de Fuca is blanketed with fog. In this picture, the Olympic Mountains protrude above the fog bank which lies to the south of Race Rocks. (Photo taken June 17, 2006 on the remote camera 5 by PB)


field trip videoThe opening scenes of this video show how dense the fog was on one trip in June to Race Rocks. The boat was guided by radar.

morning fog
Click here to see our file on the Fog Horn at Race Rocks. An early morning sunrise through the fog.
fog from remote camera fog from remote camera fog from remote camera fog from remote camera
At 10:00 AM on July4 2007, this heavy fog enveloped the island. The sun was totally obscured, even though it was a hot sunny day back in Pedder Bay. A ” fog arch” could be seen to the west. This is caused by diffraction of light by the water droplets. It continued down into the ocean. (Photo from camera 5 remote by Garry F)

See the posts in this log noting the days with fog


In some coastal areas, tree species receiving the highest amount of pollutants via fog are experiencing damage. fog islandAt Race Rocks, in foggy weather, the dried grasses will condense moisture from the atmosphere. This moisture allows the plants to recover from summer drought.On hot summer days the temperature at Race Rocks can be as high as 10 degrees C lower due to the fog compared to the adjacent shoreline of southern Vancouver Island. Below is an example of the right conditions for the creation of “Precipitation Fog”
This particular week in September of 2006 has been chosen to show how we can get “rain” recorded in the tipping bucket sensor at Race Rocks even when there is “no rain in sight” at Race Rocks.. Late Monday evening of Sept 4, 0.2 mm. of precipitation was recorded.
Fog/Dew Sept 4I recall seeing a heavy dew on the fields in Metchosin on that particular morning. At the same time, the dew point was 12.8. The humidity was 100%


The temperature was at 12.8 degrees C, so the formation of moisture would happen on surfaces on the island. Previously, the light keeper would record this as trace when doing the rain calculation.

fog Students at Race Rocks on a foggy day fog tower

Recent Posts

adventurous pups


In the morning we had a light south wind an overcast sky and a good visibility but the wind get stronger in the afternoon and changed its direction to South West with a gust around 28 knots. The air temperature was 4.3 degrees Celsius so cold and grey day with some rain


Our main concern is still the pups . They became again adventurous and changed locations: the one under our kitchen window decided to go closed to the tower followed by the young male . He just smelled the baby it was it . The injured one decided to moved towards the rocks and he went pretty far and it looks like  now he is stuck …So…We will see Tomorrow . Maybe he was attracted by the water and the high enough tide will be only Tomorrow afternoon …the question is to know if he will be strong enough to move his body and get out… Chunk didn’t come back



We finished preparing the students house. they will come for a week on Sunday or Monday depending the weather. actually we cleaned and washed the basement floor and carpets . So it is ready


3 watching boats


  1. Surviving pups Comments Off on Surviving pups
  2. Environment Canada for the weather station on the rock Comments Off on Environment Canada for the weather station on the rock
  3. Chunk attacked a pup Comments Off on Chunk attacked a pup
  4. A sea lion on the grass Comments Off on A sea lion on the grass
  5. Visitors Comments Off on Visitors
  6. Census Comments Off on Census
  7. Gulls getting ready Comments Off on Gulls getting ready
  8. A surprise: helicopter on the rock Comments Off on A surprise: helicopter on the rock
  9. Spring coming… Comments Off on Spring coming…