Was 2025 An Usual Weather Year in the Pacific Northwest?

With January 1 behind us now, it is time to examine the weather of 2025.   

Was it unusual?  Did it represent some kind of climatological extreme?

Let's check out the numbers and decide.

Starting with average temperatures,  the map below shows the difference from normal of the annual temperatures (F) over the past year.  

In general, this was a warmer-than-normal year (yellow and orange colors), with the majority of the region being within 2°F of normal (yellow and green).  About 30% of the region was 2-4F above normal.

For precipitation, the percent of normal for the entire year is shown below.  About 30% of the region was above normal, some much above normal (dark green). About 40% of the area was dry, 40-90% of normal

So, for temperature and precipitation, it was a real mixed bag, with a tendency towards modestly warmer and drier than normal conditions.

But how unusual was this year?   To gain some insights, let's check out some stations.

First, considering the annual average temperature at Olympic Airport, this year was certainly not a record, but it was relatively warm compared to the past 75 years.  A slow warming trend is noted.

Moving to eastern Washington (Ephrata), a very similar story.

So the temperature story is not exceptional:  a modestly warm, non-record year.

Next, consider precipititation; we have an issue with missing data in 2024 (29 days missing) and 2025 (6 days missing).  I worry that might have affected the earlier figures as well.  

Even with missing data, Olympia was only a little below normal in 2024 and 2025.  Very little long-term trend in precipitation

And Ephrata precipitation was near normal the last few years, with very little trend.

In short, although a bit on the dry/warm side, 2025 was really not exceptional.   Not a year of overall temperature and precipitation extremes.  Kind of a yawn. 

Yes, we had some wetter and drier periods during the year (which is not unusual), but in the end we came out a little below normal, as illustrated by the cumulative precipitation at Olympia.

Some northern WA stations, like Bellingham, came in above normal (see below)

It is good I don't have a YouTube channel; this relatively boring finding would not get me many clicks.😊

Glorious Fog, Unfortunate Inversion

 A persistent area of fog has spread over the central and southern Sound, and some of the pictures are stunning.

The 6 PM view from the Space Needle cam is simply beautiful, with some of the taller buildings extending above the murk.  The lighting of the fog from below....

From the hills east of Seattle, the fog layer spread to the Olympics, with a beautiful sunset glow above.

Picture taken by Kristi Benda.

Not to be outdone, the image from space captured by the NASA Aqua satellite this morning was extraordinary, with fog and low stratus clouds constrained by local terrain.

Why so foggy?  

Blame it on high pressure and clear skies aloft, which produce a strong inversion, in which temperature warms with height in the lower atmosphere.

Clear skies allow good radiational cooling of the surface, and high pressure aloft creates the clear skies and produces sinking air aloft, which warms the air by compression.

Want proof of the inversion?    Below is a plot of the temperature change with height at 6 PM around SeaTac Airport.

Temperatures warm from the mid-30s near the surface to about 50°F around 2000 ft.   That is a strong inversion!  Inversions are associated with great stability, which means they suppress mixing of the air in the vertical.   Good for keeping the fog in place!

Unfortunately, inversions have a major downside; they also keep pollutants in place, suppressing vertical mixing, which improves air quality near the surface.

Below are the current pollution levels (something called PM2.5), based on the PurpleAir network.

Moderate air quality at lower elevations (yellow colors) but far better at higher elevations (green colors).  

This situation should continue tomorrow, but will dissipate on Friday.

Happy New Year!