July 10, 2022

The Potential for Large Grass Fires in Eastern Washington this Summer

There is a serious wildfire threat in eastern Washington right now, with a growing potential for large, fast-moving grass fires.

For this threat to be realized, all it will take is strong winds and some careless ignition.

I found huge amounts of annual grasses when I took a drive to 
Thorp, Washington on Saturday.  Worrisome.

Ironically, the key setup was the cool, moist spring we just completed, which led to bountiful grass production east of the Cascade crest.  

The wonderful USDA Forest Service website fuelcast.net shows the situation clearly.  Below is a map of the current amount of annual herbacious plant material (such as annual grasses) in our region (I secured this from fuelcast).

Substantial fuel amounts over the Columbia Basin and the eastern slopes of the Cascades, with large areas with more the 700 pounds per acres.  That is a lot of fuel for fire.

How unusual is such accumulations of annual "fuels"?  The following graphic from fuelcast.net shows the deviation from normal of vegetative fuels, with the outline showing the Columbia Basin.  Some areas near Yakima and the eastern Cascade slopes have over 200% of normal vegetative mass (like annual grasses)

Very dangerous.

The danger was realized last week when someone started a large grass fire near Prosser (the Byron Hill Fire) that incinerated over 4000 acres (see picture below).    Fireworks ignited the fire.

The Byron Hill Fire

The threat is rapidly worsening now as the huge amount of grass/annual vegetation rapidly dries and "cures"--- a normal process that was delayed by the cool, wet weather.  With dry, warm summers, grasses are generally ready to burn by middle to late June in eastern Washington.

One can track the drying process by looking at graphs of dead fuel moisture available from the U.S. RAWS weather stations around the U.S.  Many measure 10-h dead fuel moisture for small diameter fuels (a diameter less than one inch).

As a rough rule of thumb, 10-h dry fuel moisture below 10% is a dangerous fire threat.  And it only takes roughly a day of dry weather to make such fuels a problem...that is why they are called 10-h fuels.

Below is the 10-h deal fuel moisture from the YTC-RC site northeast of Yakima for the past 90 days.   The 10-h fuel moisture goes up and down due to short rainy period, but during the dry spell in late June it dropped below 6%!

The message is clear.  With the huge amount of grasses in place now curing (drying out) and fuel moisture dropped to under 10%, there is a large threat.

And for this threat to be realized, we need some ignition source (e.g., fireworks, trash burn, cigarettes, target practice sparking on a rock, lightning, failing electrical infrastructure).  

But to get a fast-moving grass fire you also need wind.  And wind we can forecast with great skill.

For eastern Washington, there are two major wind situations to keep in mind.  The first is the strong northwesterly winds that descend the eastern slopes of the Cascade slopes, particularly during the afternoon and early evening.    There is a reason there are a lot of wind turbines just east of the Cascades!

Such winds are particularly strong during periods of unusually cool weather in western Washington after on onshore marine push.

And then there are the powerful winds associated with high pressure building to the north and northeast.  Such winds are particularly frequent and strong during late summer.  Such as event occurred during September 7-8, 2020, and resulted in a fast-burning fire that destroyed the eastern WA town of Malden (see below)

Malden Washington
Whitman Country Sheriff's Office

Time to Act is Now

With such an acute wildfire threat, anyone living near large expanses of grass should clear several hundred feet of safe space around their residence.  You should be ready to evacuate quickly, any time strong winds are forecast.

The state needs to be constantly monitoring the winds and warning people when strong winds are predicted.  And the state needs to ready fire fighting capabilities for such events.

Of course, folks need to be very careful about not starting fires.  Utilities need to ensure no branches hang over power lines and be read to de-energize powerlines in vulnerable locations.

Some advanced planning could help ensure that another Malden disaster does not occur this summer.


  1. Mow that long grass, bale it up for animal feed.

  2. Isn't it completely natural for these fires to happen every year? Why worry about it? If someone's house is next to these grasses, they should get a lawn mower and get to work, instead of complaining later.

  3. I have grass that's up to 6 feet tall in places on my forested/ grassland near Republic. But I can't see it drying out at all here this year. Very high water content in the ground right now. Next year I will have to worry about it though likely.

  4. As I type, my grass is turning a pale green in many areas and the rate of growth is slowing down as the grass dries out.

    I just mowed my lawn over the weekend and took the weed eater to the back alley as the middle median up to Fife St has tall grass that can brush up against the bottom side of cars and trucks, and the hot exhaust catalytic converters, which can potentially start a fire, and it's between several houses.

    I also pulled out the very tall grass in my flower bed this morning on the west side of my house as the iris' were getting obscured by the grasses growing in the bed. Much better now.

    I live in the city and most of us do not water our lawns much if at all during the summer months, and some years, they turn brown, other years, they never quite turn fully brown and many that I see are still mostly green still, thanks to the cooler and wetter spring we just went through.

  5. Near me there is land that needs a herd of goats to clean it up. Some places, not suitable for harvest, can be cut with a rotary mower and mulched in-place. This will be a dangerous summer.
    There needs to be a major push to reduce ignitions.

    1. Goats are browsers not grazes. You need sheep.

  6. Management of land (and fire risk) is going to become a much bigger challenge in the coming decade, as the costs of gasoline and diesel becomes much higher.

    1. 1. What does the cost of gasoline have to do with management of land and fire risk?
      2. I have tried, but I am not able to predict the future. How do you know what the price of certain things will be in the future?

  7. With rising atmospheric CO2 levels, the photosynthetic process is guaranteeing that we will be experiencing impressive increases in both vegetative growth and the drought resistance of the added vegetation. And the increase in these two factors won't peak until atmospheric CO2 levels double from current levels. In short, this problem will not go away and it is imperative that we deal with this issue much more aggressively than we are.

    On the plus side, we are seeing an equally large increase in food crop production.

  8. Cliff, do you still think we're gonna have cooler then normal summers? La Nina has weakened to neutral now.

    1. The model-based ENSO outlook forecasts a continuation of the La NiƱa event with moderate probability (52% chance) during Jul-Sep 2022, continuing into boreal fall and winter with 51-59% likelihood.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

New Podcast: Memorial Day Weekend Forecast and More on Western Washington Wildfires

This weekend will be a mixed bag west of the Cascade Crest but warm over eastern Washington.  The predicted high temperatures for the next f...