My Least Favorite Weather Phenom

Tule Fog

After coming back from a few days of 60 degrees and gorgeous blue skies on the coast, this morning’s tule fog was a bit of a downer. It’s easy enough to deal with as long as you have a powerful lighting set-up, but the feeling of riding through gray soup leaves a bit to be desired. Statistically, tule fog is quite dangerous and it’s the cause of many collisions, so it stands to reason that bicyclists should use very good lights if they choose to ride through this stuff. Here’s more on tule fog from Wikipedia:

Tule fog (pronounced /ˈtuːliː/) is a thick ground fog that settles in the San Joaquin Valley and Sacramento Valley areas of California’s Great Central Valley. Tule fog forms during the late fall and winter (California’s rainy season) after the first significant rainfall. The official time frame for tule fog to form is from November 1 to March 31. This phenomenon is named after the tule grass wetlands (tulares) of the Central Valley. Accidents caused by the tule fog are the leading cause of weather-related casualties in California.

Stay visible and safe out there!

11 Responses to “My Least Favorite Weather Phenom”

  • Micheal Blue says:

    I rode through a fog like that ones. During dusk. The rear light I had (a cheap LED Planet Bike) was useless. After that experience I bought the 400-lumen Dinotte rear light. That produces enough photons to even push the bike forward. Of course, normally I run it on low power. For the front I have a B&M Cyo Plus light and also LED Lenser P7 flashlight attached with a hose clamp to the handlebars (it’s a be-seen light). The worst weather for me is a strong headwind, which is (unfortunately) a relatively frequent occurence in Toronto.

  • Fergie348 says:

    The fog was so thick this morning that I couldn’t see the end of my driveway. I don’t even have a driveway, more like a parking space.. NWS said it came down the Carquinez strait overnight from the Sacramento valley. I had all my lights on for this morning’s commute..

  • Alan says:


    It sounds as if our fog poured over into your area today. Sorry! :-)

  • Paul says:

    “Accidents caused by the tule fog are the leading cause of weather-related casualties in California.”? How can a leading cause be considered an accident? It seems that it should be expected. In addition, there were no “weather-related casualties” a century ago, but there was just as much tule fog. Seems like the leading cause of casualities is the motor-vehicle.

  • Alan says:


    I hear you; it’s irksome. It’s standard boilerplate language you see everywhere in the press. You may have noticed I used the word “collision” instead.


  • John Riley says:

    It was 60 up there? We barely break 50 in the city.

  • John says:

    I love riding through the fog when it gets nice and thick in Portland (reminds me of my tule fog roots in California). But then I also have B&M lights on the front and back, driven from a dyno so I know I’m seen as well as possible.

    The weather condition that will always get the lion’s share of my hate is wind, especially since it’s rarely at my back. Cold, Fog, Snow, Ice, Rain, Heat. None of those bother me like wind.

  • Alan says:

    @John Riley

    Well, it was actually 59F, but close enough. ;-) The last time we were in Mendo in January we had the same weather; gorgeous….

  • Fergie says:

    All other bad weather seems to just happen. Wind for some reason seems personal. I can’t count the number of rides where the wind seems to follow you around a loop or changes on an out and back so you always have a headwind. Grr..

    @Alan, all is forgiven as long as you don’t send the heat in from Sacto in the summertime ;)

  • John_in_NH says:

    I have never experienced such a fog, in way upstate NY we do get some good soup fog, but I think it is this bad. I have enough lights that it is no problem even on the rural sections, but I actually really love late night fog cycling through the downtown and dense residential areas. Its like a light snow, everything is quiet and you feel a sense of calm (I do) more so than usual :)

    hail and freezing rain is the worse to ride in, headwinds are next but very very close

  • Teddy says:

    Fog has always been a concern for me. Especially on anything technical and fast.
    I don’t have very extensive experience riding in the fog, but the worst thing about it for me is when my glasses collect water.

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