Hot/Dry Summer and Minimal Wildfire over Washington State. WHY?

Wildfire acreage has been running far below normal over Washington State--- in fact, over the whole Pacific Northwest.

To demonstrate this, here are the latest WA DNR wildfire acreage statistics for Washington as of August 23.  2025 is well below normal.

All years show acres burned through August 23.

Or look at the map of large fires from the Northwest Fire Coordination Center (below).

Only three fires, and the two fires in Washington have been burning for a while and are only slowly growing.

In contrast to a lackluster wildfire season, we have had a warm, dry summer.  

Check the deviation from normal for temperature (left panel) and precipitation (right panel) for the last 90 days over the Northwest (below).

Most of the region has been warmer than normal (yellow, orange, and red colors).  It has been drier than normal over the region, except for the Olympic foothills and south-central Oregon. 

The media (e.g., the Seattle Times Climate Lab) and others have been suggesting that this would be a big wildfire year due to the warmth and dryness.  They were wrong. And yes, they suggested a major role for climate change in the predicted fires.

How did they get this wrong and why?  

It turns out that the connection between wildfires and meteorology is a bit more complicated than some media and climate advocacy groups suggest, and that simplistic arguments are simply inadequate.

Question 1:  Why so dry and warm this summer?  

The best science suggests that human-caused global warming has warmed the region by about 2°F and only caused slight drying. 

Why so warm/dry this summer?

Below is the difference of sea-level pressure from normal from June 1 through August 22.   Higher pressure than normal over the region, particularly offshore.

At 500 hPa (about 18000 ft, see below), the offshore high was very evident (red colors).  This pattern is a warm and dry one for our region, with sinking air aloft.   

No wonder we have been warmer and drier this summer.   There is no evidence that such a pattern has anything to do with global warming (I have studied and published on this exact issue).

Question 2: Why so little wildfire activity when it has been warm and dry?

First, with the dry conditions during the late spring and summer, seasonal grass growth, an important fuel for regional wildfires, has been less than normal, which works against wildfire activity.

Below is a graphic from the Forest Service FuelCast website, showing below-normal values (yellow) over most of the region.

Second, lightning activity has been less over most of Washington this summer due to the dry conditions.   Below is the difference in lightning between this summer and last summer over Washington, southern BC, and northern Oregon.

Most of the area has had less lightning this year, particularly the fire-prone eastern slopes of the Cascades. (blue colors indicate less lightning).

Image produced by Katrina Virts, Research Scientist, SNWG MO Deputy Project Scientist/Assessment LeadNASA MSFC Office of Data Science and Informatics (ODSI), The University of Alabama in Huntsville

Lightning is an important initiator of regional wildfires, particularly at higher elevations that are difficult for firefighters to access.    This is important.

Third, with high pressure offshore, the winds have been affected, since pressure controls the winds.  Strong downslope winds on the eastern side of the Cascades are often associated with cool air moving into western Washington behind upper-level troughs, something suppressed this year because of the high pressure.

Since the strong winds can contribute to the rapid spread of wildfire, lesser winds reduce the wildfire threat.  Take a look at the sustained winds at Wenatchee, WA, last summer (top) and this summer (bottom).  Fewer strong winds this summer (the red line is 23 kt)

Fourth,  the technology of wildfire firefighting has advanced dramatically during the past few years.  A series of high-resolution cameras, with AI interpretation, has been distributed over the region.

Increased use of high-resolution satellite data is also providing far better fire intelligence.  Drones are being used to discover and surveil fires.

Increased coordination with aircraft used for suppression has allowed more rapid response to new wildfires.

Analagous to the  Ukraine war, new technology has radically changed the battle against wildfires.  

The bottom line is that the idea of warmer and drier means more wildfire acreage is simplistic.  Other factors can be equally or more important.

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3D Northwest Heat

 We are now in a short warm spell with temperatures getting into the mid 80s to lower 90s in western Washington.  Cooler weather (and some rain) will arrive next week.

 But for me, one of the most fascinating aspects of our warmth is how three-dimensional it is.  How spatially varying the heat can be.

Let me show you, by starting with yesterday's highs (below). Mid-80s around Seattle, 70s and low 80s over Northwest Washington, around 100F in the Willamette Valley, and upper 90s in the Columbia Basin.   An interesting feature is the near 100°F in the higher terrain between Olympia and the coast,.

In western Washington, the influence of the cool Pacific and inland waters results in cold air near the surface, but warmer temperatures right above.  This is particularly true when (like yesterday) there is easterly  (from the east) flow aloft moving warmer air from eastern Washington towards the west.

Yesterday (Friday) morning, this situation was so profound that there was an inversion (temperature increasing with height) above Seattle, something illustrated by the temperatures above SeaTac Airport at 8 AM (below).  Temperatures in the mid-60s near the surface, but 70s above 2200 ft.  

A profound inversion from 1000 to 2500 ft (more than 10 degrees).  I bet morning hikers noticed this warming with height!

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This morning at 7 AM, the inversion was even stronger  (see below), going from 67°F to 79°F above 1500 ft.

The inversion weakened during the day as solar heating warmed the surface.

A temperature inversion can act as an atmospheric lens for weather radar beams, causing  the radar beam to bend downward to the surface, which acts as a target.

This inversion bending of radar explains the huge number of false radar echoes off our coast right now (see below).  The radar beam hits the ocean surface and then is reflected back. 

Looks like a lot of rain out there...in reality there is nothing.

When we have inversion conditions, maps of temperature can get jarring, such as this morning at 7 AM in the Cascade foothills near North Bend.  Around 70°F on ridgetops but lower 50s and 40s in valleys.

According to the latest National Weather Service forecast, the warmth will continue over the weekend, with cooling by mid-week.  Possible rain next weekend.

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