February 13, 2019

Will This Be The Coldest February in Sea-Tac History?

We have already broken one major record:  Seattle-Tacoma Airport had its snowiest February since record keeping began during the late 1940s:  20.2 inches.  Impressive.

But I think there is an excellent chance we will break another record, this time for cold.  

Specifically, I think there is a very good change that Sea-Tac Airport will experience the coldest February on record as well....and that is really a very impressive record.

Hold your horses, some of you might exclaim!  We are only half way through the month!  Who knows what will happen?

True.  But the first half of the month has been very cold, we have excellent forecast skill for the next week, our best guidance suggests a very cold pattern remaining in place, and this is a very short month.

In Seattle, our high temperatures have been running about 15 degrees below normal, with our high temperatures barely making a normal minimums. (see below, cyan is average low, purple average high)
The National Weather Services Climate Forecast System Model  (CFSv2) is predicting unusually cold temperatures for the rest of the month (see below).  The cold anomaly (difference from normal) is so large, it is off the scale! (dark blue is much colder than normal)

The NOAA/NWS Climate Prediction Center, which tries to bring in multiple types of guidance, is going an amazing cold anomaly for the last week of the month (see below).  I am getting chilled just looking at it.

So will we experience the coldest February in Seattle (Sea-Tac's) history? 

Checking official NOAA records, the coldest Februaries at Sea Tac were 35.6 F in 1956 and 35.9F in 1989 (these are daily mean temperatures, calculated by averaging the daily highs and lows).   To estimate this month, I start with knowing the actual highs and lows through today (almost halfway there!), and then complete the month using the forecasts from IBM/weather.com.  Their forecasts are excellent, using statistics to combine many sources of weather information. 

You will not believe what I got:  34.17F for the February average.   We not only beat the record, but shatter it.  

Whatever happens, we are almost guaranteed to be in one of the top five coldest Februaries for Sea-Tac.

Why so cold?  Because the atmosphere is locked into an upper-level flow configuration of troughing (low pressure) over the western U.S. (see examples from last Saturday and this Friday morning--they look pretty similar!). 


And talking about cold, temperatures will drop below freezing tonight, particularly in a few hours when the skies clear further.   Slush will freeze into ice, but quite frankly wet slush is just as slippery as ice.  The only good thing about slush is that the weight of cars can push it out of the way, often allowing some traction.  And the slow warm up should greatly lessen the chances of flooding or landslides.


  1. Replies
    1. The birds seem to think it IS spring already. Many birds have returned much earlier in the year than I've seen in the past.

  2. The first half of February at Sea-Tac will average approximately 34 degrees.So the last half needs to average around 37 or less for the record to be broken.Barring another major arctic blast,I don't think the latter half will be nearly as cold as the first half,so your 34 degree estimate is probably a little too much on the cold side.I think it will be close whether the record gets broken.By the way, the coldest Feb for all Seattle locations was 35.1 in 1891,the year temp data first began to be recorded.

  3. Wow! Good stuff. Cliff, what is the current average mean temperature for the month? Thanks for all your work during the snow events. It is appreciated!

  4. Took a little bit to get my bearings on the model images but I found Vancouver Island then I got it. Upper level trouughing. Does that mean mixing in colder upper level air in a persistent trough which brings it down to surface?

  5. Thank you for all the great info Cliff. I love reading your blog!!

  6. So, why has this trough been in the wrong place (too far west) for this period?

    At the same time, Alaska has been too warm.

  7. For those of you who have been waiting breathlessly, a weak El Nino condition has finally been declared:

    "Overall, these features are consistent with borderline, weak El Nino conditions."

    The probability that this will continue through the spring in the Northern Hemisphere is now assessed as only slightly above a toss-up (~55%).


  8. Big Blue Blob...since the snow and ice have evaporated, there are alot more budding and bulb growth events...little does the plant world know what's in store.

  9. Is this pattern typical for even a weak El Nino? If memory serves, it doesn't appear so.

  10. For those who are tempted to conclude these extended cold outbreaks signify there is no global warming:



  11. Where would one find data for neighborhood snowfall totals on a day-by-day basis?

  12. Cliff (or one of your expert followers): would you pls blog about the composition (temperature, density, etc) of current snowpack vs historical, and the implications for the melt out this spring/summer? I'm wondering... Even if we have a warmer and drier spring/summer (again), would this snowpack melt out slower because of its composition? Thanks!

  13. This weather is a drag, not a complainer typically but that neast wind is about as welcome now as the canadians when they flood into Bellingham costco single file like a burlington northern train to hog the best parking and fuel up on sunday morning, the socially stunted potpourri culture will hog the aisles and would never swerve or yield the way, once they drove over the toes of a guy I know, was the wrong thing to do, he’s very dramatic and loud. Miss Ying Ghou Chung heard an earful

  14. I wish that cold air and snow would dip a bit South into the mid-Willamette Valley!

  15. Isn't this the sort of event predicted by the "lazy jetstream" hypothesis?

    While I understand this isn't a validation but it is a data point?


  16. Does this mean that the Arctic is exceptionally warm in compensation? The CFSv2 map doesn't depict the pole well, but the northern edges of the picture look very red.

  17. From Bow, WA .. 6:00 pm Thursday .. rain (light) and melting. Plowed roads good, slushy roads slushy. Reporting rock about to reappear (about an inch of snow to go I think) and resume duty. Drivers and good sams doing good.

  18. Hi Cliff: I well remember February of 1989. What I remember most was the mildness which preceded the deep-freeze in early February. The temperature went from 60 degrees to 14 degree is the space of 40 hours. I also seem to recall that the last week of February was mild and wet before we had more snow and cold during the first few days of March. I imagine that, in the absence of the mild spell during the last week of the month, February of 1989 would have been even colder than it already was. Happy Valentines day to you and yours.

  19. Cliff, Thank you for the great coverage over the past week. I’m curious if any other readers have noticed two colors of snow in the past week. In the Port Angeles to Sol Duc Valley area the snow that fell on Friday the 8th has a brownish tinge and looked a little like pancake batter. The subsequent snowfalls were a normal “snow” white.

  20. Wet slush as slippery as ice? Let's see some data! ;) By the way that new "verify" process tells me to stay away from now on. Adios


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