Every ten years the National weather service tallies what are known as normals. They are the averages for climate for each specific recording location. I’ve been anxiously awaiting this years numbers. They represent the climate averages from 1991-2020. ( Our previous record was 1981-2010 ). The NOAA uses these thirty year records to not only show the recorded averages they can also predict trends. In our current state of climate change this can be very important. It definitely shows trends.
Summers are hotter, drier, and longer
The records are kept at the NOAA PDX the Portland Airport. Official records have been kept there since 1940. Before that records were kept when the airport was on Swan Island. Records show that in that time our average annual temperature has risen approximately 2 degrees fahrenheit. The majority of that heating has occurred since 1970. Records for the past 70 years have also shown dramatic increases in both annual and daily temperatures as well as ultimate high temperatures.Courtesy NOAA
Check out the 2010’s temperatures- temperatures above 90 have spiked. We now average 14 days above 90ºF. The most conspicuous rise is in temperatures per annum is above 95ºF. Surprisingly, during this period Portland, did not exceed its all time temperature record of 107ºF (set in 1965 and twice in 1981). This is surprising as during this same period Seattle, Boise, San Francisco, and Los Angeles all exceeded their highest temperatures ever recorded. I wouldn’t be surprised to see that record broken in the next several years. Could 109ºF be in our future? We shall see.
What is obvious is that we are getting warmer earlier in the year, May went from >1 day above 90ºF to averaging 3 days currently. There is also an increase in record high temperatures during June. And our average annual temperature now peaks in late July to mid-August with an average high of 83ºF. Up 3 degrees from the previous averages.
Average low temperatures have shown a dramatic increase too. This is less conspicuous to people because we are mostly asleep. But warming overnight lows is a hallmark of global warming and we are seeing that. 2019 broke the record 63 days with lows above 60ºF.
We’re seeing the climate we have lived in for the past 30 years.
Winter temperatures have warmed significantly also, and in less than 20 years we have set and then exceeded the record for warmest winter ultimate low 3 times. The last was the winter of 2019/2020 when our lowest recorded temperature was just 28ºF. In fact, the average annual low at Portland International is now 21.3ºF. (1990- 2020)Thats a significant move from the previous average of 19.6ºF. If you are a gardener that seems like a very dramatic jump from zone 8b to zone 9a. In reality we are just now viewing the weather that we’ve already had. Weather over the long term has edged up but we can still expect a true arctic blast ( below 20ºF) every few years. An example of this was our February snow/ice event. Though the lowest temperature was just 24ºF- not that cold. Interestingly 23, 0f the past 30 years we have had zone 9 winters, so any change in our zone designation (though moot cause its the past 30 years) should not be a surprise.
Wetter earlier then drier
Rainfall is just as interesting. The Portland area increased its average annual amount just slightly to 36.78″ from a previous 36.03. More rainfall is occurring earlier in October. This can primarily be seen as an increase in atmospheric river events earlier in fall. November still captures the highest average rain total of 5.67″. But the overall trend is for more concentrated precipitation in late fall and early winter that slips off slightly from January on. A very conspicuous change to our rainfall is in significantly drier summers. Previously July totaled an average of .67″ and August was .85″. Hotter summers are taking their toll. July has slipped to just an average of .50″ and August just .54″ thats barely over an inch of rain in 62 days during our hottest and most evaporative time of the year.
So, the climate normals show several conspicuous trends. Our climate is warming over all. Winters are warmer with rainfall more concentrated between October and February. Our average annual low temperature has inched up to 21.3ºF. Summer is starting earlier in May and continuing until September. These warmer months are also drier with just .50″ and 54″ of rain in July and August respectively. Not only high temperatures are increasing but overnight lows as well. While none of this is a surprise its good to get confirmation of what we have all been experiencing. Climate change is here and its accelerating.