For more than a week, weather enthusiasts have fixated on the chilly upper-level trough that is currently entering the Pacific Northwest and will stick with us for the coming week. Snow levels will drop to 1000’ at times, and a few slushy flakes could be seen even at the lowest elevations.

But I’ve long felt that false spring – here defined as a stretch of warm and (usually) dry weather before March 1 – is a more noteworthy phenomenon than slushy late winter slop. Especially in an El Niño season, it’s one of the signature patterns to look for.

We DID get a couple spring-like days last week, especially Thursday and Friday when PDX hit 60 and 63. My entire household was either gardening or sunbathing on both days. But while this brief taste of spring was very pleasant, it didn’t even make the top 20 when it comes to February warm spell history.

It turns out that a stretch of 3 or more days in the 60s in mid/late February is not too unusual, occurring in nearly one out of four years. Hitting 65 is harder, though…and 70 degrees is a very rare occurrence. To analyze the data, I looked at Februarys that had at least a 3-day stretch of 60+. Then I created a 3-tier system for ranking February warm events based on both duration and intensity.

Events are listed according to year and high temps, and the date range is to the right of the year. For example, “20-23” means that the false spring began on February 20 and ended on the 23rd.

 

The criteria are as follows:

Gold. At least 3 consecutive days 65+, OR 5 consecutive 60+ including 3 65+ days.

Silver. At least 3 consecutive 60+ including one or two 65+, OR 5 days in low 60s within a 7-day period.

Bronze. At least 3 consecutive days in low 60s

GOLD TIER

 

1968 22-29

60, 63, 63, 66, 68, 67, 70, 68

 

1986 24-28

68, 60, 65, 65, 62

 

1988 26-29

67, 66, 71, 64

 

1991 23-28

60, 62, 66, 67, 66, 63

 

SILVER TIER

 

1964 9-11

62, 65, 60

 

1973 20-25

63, 62, 60, 60, 61, 63

 

1977 14-19

63, 62, 54, 60, 68, 66

 

1990 24-28

62, 63, 60, 61, 64

 

1992 24-28

60, 64, 62, 63, 60

 

1995 18-23

62, 61, 62, 63, 58, 67

 

2005 21-27

60, 62, 63, 64, 56, 61, 65

 

2015 12-17

63, 56, 61, 64, 61, 63

 

2022 11-13

67, 63, 63

 

BRONZE TIER

 

1941 19-23

60, 60, 61, 60

 

1970 24-27

62, 64, 62, 60

 

1971 10-13

60, 62, 60, 60

 

1996 13-15

60, 60, 63

 

2008 27-29

61, 63, 63

 

2016 7-10

62, 62, 60, 62

 

2016 24-26

62, 64, 60

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Some notes:

1. Some of these warm events may have included one of more cloudy/wet days; I didn’t take the time to check.

2. February warm waves are very much a mid/late month phenomenon. We can have one or two 60-degree days at the beginning, like we did this year. But the sun is still too weak for it to be a “sustainable” pattern.

3. Only once have we had two significant warm events in the same month (2016). This is unsurprising because it requires a bare minimum of 6 warm days, not including any other isolated 60s. (February 2016 had a record 9 such days!)

4. It’s not hard at all to hit 60 in February; a majority of years have at least one warm day. But 65 is a different story; only 12 of the past 85 years have hit that mark. 70 is extremely rare, occurring only twice in PDX history.

5. The “gold” warm spells are not distributed equally throughout history. There were no gold events in the first 27 years of airport records. Then we had four such events in a 24-year period, including three of them just between 1986 and 1991! Then no more gold for the past 33 years. This uneven spacing may have contributed to locals “forgetting” what the late February sun is capable of.

6. Warm spells have not gotten more frequent in the last couple decades. This mirrors the overall climate trend, where February is the only month not to be trending warmer over time. Sure, we had record warmth in 2015 & 2016…but they were offset by the dismally chilly 2019, plus several other cool Februarys during the 2011-20 decade.

7.  The 2022 false spring was the first time we ever made silver before Valentine’s Day. More on the implications below.

 

So where do we go from here? I think the recent trend of more snow and cool airmasses late in the season is just that: a brief trend. Nearly every other month is setting records for warmth, whether in terms of averages or individual heat waves. Sooner or later the chickens will come home to roost in February as well.

All we need is for a STRONG ridge to set up shop in the 2nd half of the month, to put us at least in the “silver business.” That hasn’t happened since 2016. And even the ridges those two years were not quite ideal in terms of timing and 850mb temps. The first warm spell in February 2016 was historically strong and warm in the middle and upper atmosphere. But it came too early in the month for the sun to fully overcome valley inversions. Had it happened two weeks later, places like Portland and Salem would have likely been in the upper 60s or even flirting with 70, for a few days.

Anyway…the point is that it CAN, on occasion, turn magically warm under the February sun. But everything has to line up with perfect timing and position for it to happen. Nonetheless, we are probably due for an epic “Gold Tier” false spring in the not-too-distant future.

At least we got a little taste of the sun angle magic this February. By the way, don’t let the current cool pattern get your spirits down. The seasonal outlook for spring proper (March-May) is looking very hopeful for the Pacific Northwest:

 

Happy almost springtime!

Karl